Improving Urban Air Quality in South Asia by Reducing Emissions ...

Improving Urban Air Quality inSouth Asia by Reducing Emissionsfrom Two-Stroke Engine Vehicles

Masami KojimaCarter BrandonJitendra Shah

December 2000

THEWORLDBANK

Cover: Traffic images of South Asia. All images property of the World Bank.

The International Bank for Reconstructionand Development/THE WORLD BANK1818 H Street, N.W.Washington, D.C. 20433, U.S.A.

Manufactured in the United States of AmericaFirst Printing December 2000

The findings, interpretations, and conclusions expressed in this paper are entirely those of the author(s) andshould not be attributed in any manner to the World Bank, to its affiliated organizations, or to member of itsBoard of executive Directors or the countries they represent. The World Bank does not guarantee the accuracy ofthe data included in this publication and accepts no responsibility for any consequence of their use. The bound-aries, colors, denominations and any other information shown on any map in this volume do not imply, on thepart of the World Bank Group any judgment on the legal status of any territory, or any endorsement or accep-tance of such boundaries.

Masami Kojima is a Senior Energy/Environment Specialist in the Oil, Gas, and Chemicals Department of theWorld Bank; Carter Brandon is a Lead Environmental Economist, and Jitendra Shah is a Senior EnvironmentalEngineer, both of the South Asia Environment Unit of the World Bank.

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Foreword vii

Abstract ix

Acknowledgments ix

Abbreviations xi

Executive Summary 1

The Problem of Emissions from Two-Stroke Engine Vehicles 1Emissions from two-stroke engines pose a danger to public health 1Poor vehicle maintenance, misuse of lubricant, and adulteration of gasoline exacerbateemissions 2

Reducing Emissions from Two-Stroke Engines 2Measures targeted at the existing fleet of two-stroke vehicles 2Measures targeted at the environmental performance of new two-stroke vehicles 3

Replacing Two-Stroke Gasoline Engines 3Four-stroke engines 3Vehicles powered by liquefied petroleum gas 4Vehicles powered by compressed natural gas 4Electric vehicles 4

Standards and Enforcement 4

Chapter 1 Understanding the Problem of Two-Stroke Engine Emissions 7The Role of Two- and Three-Wheel Vehicles in South Asia 8Types of Emissions 9Factors Exacerbating Emission 10

Misuse of lubricant 10Inadequate vehicle maintenance 11Adulteration of gasoline 11Lack of catalytic converters 11

Health Impact of Emissions 12Effect of Emissions on Global Warming 12

iv Improving Urban Air Quality in South Asia by Reducing Emissions from Two-Stroke Engine Vehicles

Chapter 2 Reducing Emissions from Two-Stroke Engine Vehicles 13Declines in Emissions 13Improving Gasoline Quality 15Improving Lubricant Use 15

Standards for lubricants 15Using the correct concentration of lubricant 15Using low-smoke lubricant 16Metering lubricant 16

Improving Vehicle Design 16Installing catalytic converters 17Reducing scavenging losses 18

Improving Maintenance 18

Chapter 3 Alternatives to Two-Stroke Gasoline Engines 21Four-Stroke Gasoline Engines 21Vehicles Powered by Liquefied Petroleum Gas 22Vehicles Powered by Compressed Natural Gas 22Electric Vehicles 23

Chapter 4 Policy Options 25Emission-Based Policies 25

Monitoring emissions 25Repairing vehicles that fail inspection 26

Technology-Specific Policies 26Banning all two-stroke engines 27More selective bans 28

Fiscal and Trade Policy Options 28Tax incentives for vehicle renewal 28Offering cash payments for older vehicles to remove them from the road 28Ensuring adequate credit 29Liberalizing trade in new vehicles 29

Public Education 29Future Directions 29

��A Health Impact of Air Pollution 31B Improving Particulate Sampling of Two-Stroke Engine Vehicles 35C Analytical Tools for Cost-Benefit Analysis 39D Reports Prepared under the South Asia Two-Stroke Engine Initiative 41

Notes 43

References and Selected Bibliography 45

Boxes

1 Reducing pollution while saving money 112 Emission standards from around the world 173 Reducing scavenging losses in two-stroke engines 194 Converting diesel three-wheelers to electric Tempos in Kathmandu 245 The role of the supreme court in air quality management in Delhi 276 Reducing emissions and improving performance through free inspection and maintenance clinics

in Delhi 30

vContents

Figure

1 Number of vehicles in Delhi by type, 1971–96 7

Tables

1 Distribution of vehicles by type, selected South Asian countries 82 Emissions from uncontrolled motorcycles, 1970s (grams per kilometer except where otherwise

indicated) 103 Emissions from selected Bangladeshi 2-stroke 3-wheelers (grams per kilometer) 104 Emission standards for gasoline-powered two-wheelers in Taiwan (China), 1988–2003 135 Emission standards for gasoline-powered two- and three-wheelers in India, 1991–2000 (grams per

kilometer) 146 Particulate matter emission factors for two-wheelers in India 147 Relation between lubricant content and emissions by uncontrolled motorcycles 168 Retail prices of lubricants in India, March 2000 (Indian rupees) 169 Particulate matter emission factors for motorcycles in Bangkok (grams per kilometer, except where

otherwise indicated) 1710 Fuel economy of two-stroke and four-stroke engine vehicles 21

A1 Experimental particulate emission results 36

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Vehicles are one of the dominant sources ofurban air pollution in South Asia. While thisproblem is common to growing metropoli-

tan areas throughout the world, it is particularlysevere in South Asia, where over half of all vehiclesare two- and three-wheel vehicles operating on two-stroke engines.

This report analyzes different technical andpolicy options for reducing emissions from two-stroke engines. As the study emphasizes, it isimportant to understand not only the cost-effective-

ness and feasibility of enforcing different mitigationmeasures but also the socioeconomic implicationsof those measures. We hope this report will stimu-late the debate on these issues and helppolicymakers arrive at informed decisions abouthow to tackle this source of urban air pollution.

Richard AckermannDirector, Environment

South Asia Region

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While vehicular air pollution is commonto growing metropolitan areas throughout the world, it is particularly severe

in South Asia, where about half of all vehicles aretwo- and three-wheel vehicles with two-stroke en-gines. This report analyzes different technical andpolicy options for reducing emissions from two-stroke engines. Precisely because two-stroke enginevehicles are so numerous and popular, an policydecision to address emissions from these vehiclesmust take into account the socioeconomic conse-quences of such a decision. While a large-scaleimmediate ban on gasoline-powered two-strokeengine vehicles would be extremely difficult andcostly, numerous small and cost-effective improve-

ments are available. Two immediate simple solu-tions—using the correct type and concentration oflubricant and carrying out regular maintenance—would significantly reduce emissions fromtwo-stroke engines while saving drivers money andultimately improving air quality. Promoting these“win-win” measures requires building public aware-ness by disseminating information on the healthimpact of emissions; the types of engines, fuel, andlubricant that reduce emissions; the importance ofregular maintenance; and the advantages and disad-vantages of various measures for mitigating airpollution. Partnerships among government, industry,and the public will continue to be crucial to bring aboutthe changes required to achieve air quality goals.

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This report summarizes the findings of the regional Two-Stroke Engine Initiative carriedout by the South Asia Environment Unit.

This initiative assessed the current state of pollu-tion from two-stroke engines and evaluateddifferent policy and technology options for curbingemissions from two- and three-wheel vehicles.

Masami Kojima of the World Bank’s Oil, Gas, andChemicals Department (Global Products Group)and Carter Brandon and Jitendra Shah of the WorldBank’s South Asia Environment Unit prepared thisreport under the guidance of Richard Ackermann,Environment Director, South Asia Region. Fundingfor this report, including for research and findingsreferenced herein, has been provided by the Gov-ernments of Denmark, Norway, and the United

Kingdom, and the joint UNDP/World Bank EnergySector Management Assistance Programme(ESMAP).

The authors thank N. V. Iyer of the Society ofIndian Automobile Manufacturers and Bajaj AutoLtd. for his extensive comments and technical in-puts. The report also benefited from constructivecomments by Maureen Cropper and Ken Gwilliamof the World Bank. The authors thank the WorldBank staff who prepared the background paperslisted in annex D and would like to express theirthanks to Barbara Karni for editorial assistance andJames Cantrell for desktop publishing. The conclu-sions and recommendations of this report are solelythose of the authors.

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API American Petroleum InstituteARAI Automotive Research Association of IndiaCNG Compressed natural gasCVS Constant volume samplingECE Economic Commission for EuropeESMAP Joint UNDP/World Bank Energy Sector Management Assistance ProgrammeFTP Federal test procedure (in the United States)IPIECA International Petroleum Industry Environmental Conservation AssociationISO International Organization for StandardizationJASO Japanese Standards OrganizationLPG Liquefied petroleum gasPM2.5 Particulate matter with an aerodynamic diameter of less than 2.5 micronsPM10 Particulate matter with an aerodynamic diameter of less than 10 micronsRON Research octane numberSIAM Society of Indian Automobile ManufacturersUNDP United Nations Development ProgrammeVAPIS Vehicular Air Pollution Information System

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Two-stroke engine vehicles are ubiquitousin South Asian cities, where they consti-tute approximately half of the total vehicle

population—60 percent in India—and contributesignificantly to urban air pollution. The serioushealth effects of this polluted air, breathed by 350million people, make urban air quality manage-ment an important policy concern. This reportaddresses the technical, economic, and policyissues related to controlling air pollution fromtwo-stroke engine vehicles.

In the past few years governments and vehiclemanufacturers in the region have started toaddress the two-stroke engine issue. India, whichhas tightened its emissions control regulations, isinvesting in improved monitoring and enforce-ment programs and has taken steps to improvelubricants used in two-stroke engines. Delhi hasprovided financial incentives to owners to replaceold three-wheel vehicles with new ones. Parallelto these government programs, two-stroke vehiclemanufacturers, aware that the regional market forthese vehicles is under threat, have contributed toprograms to improve vehicle maintenance andhave begun to bring alternative engine technolo-gies to the market. This report pulls together someof the lessons learned to date across South Asia.

The Problem of Emissions from Two-Stroke Engine Vehicles

Emissions from the large and rapidly growingnumber of two- and three-wheel vehicles are a

major source of air pollution in South Asia.Because they are less expensive than other ve-hicles, two- and three-wheelers play an importantrole in the transport market in South Asia andaccount for at least half of all vehicles in mostcountries in the region.

Two-wheel vehicles, which include mopeds,scooters, and motorcycles, are used mostly forpersonal transportation. Three-wheel vehicles,which include small taxis such as autorickshawsand larger vehicles that hold as many as a dozenpassengers, are used commercially. Until this year,nearly all three-wheelers and the majority of thetwo-wheelers had two-stroke engines. Apart fromemissions considerations, these two-stroke enginevehicles are much noisier than their four-strokeequivalents—an issue that draws much attentionin South Asian cities, but is beyond the scope ofthis paper.

Emissions from two-stroke engines pose a danger topublic health

The most critical pollutant in South Asia in termsof public health impacts is fine particulate mat-ter.1 Fine particles have been shown in studies in anumber of cities around the world to have serioushealth effects, including premature mortality andsuch nonfatal effects as respiratory symptoms,exacerbation of asthma, and changes in lungfunction. Vehicle emissions of fine particles isparticularly harmful because they occur nearground level, close to where people live and work.

2 Improving Urban Air Quality in South Asia by Reducing Emissions from Two-Stroke Engine Vehicles

Until recently new two-stroke engines emitted as muchas an order of magnitude more particulate matter thanfour-stroke engines of similar size. When vehicle age,maintenance, lubricant, and fuel quality are takeninto account, two-stroke engines in South Asiaprobably emit particulate matter at an even higherfactor.

Two-stroke engines typically have a lower fuelefficiency than four-stroke engines, with as muchas 15–40 percent of the fuel-air mixture escapingfrom the engine through the exhaust port. These“scavenging losses” contain a high level ofunburned gasoline and lubricant, which increasesemissions of hydrocarbons and organic lead ifgasoline is still leaded.2 Some of the incompletelyburned lubricant and heavier portions of gasolineare emitted as small oil droplets, which in turnincrease visible smoke and particulate emissions.

Poor vehicle maintenance, misuse of lubricant, andadulteration of gasoline exacerbate emissions

The age and poor maintenance of many two- andthree-wheelers in the region increase emissionswell above any applicable standards. In addition,many drivers use lubricants of poor quality,leading to two distinct but related problems:� Many drivers in South Asia use widely

available straight mineral oil or new orrecycled four-stroke engine oil rather than thespecially formulated 2T oil recommended byvehicle manufacturers. These oils build up inthe engine, increasing emissions.

� Drivers also use excessive quantities oflubricant. Some drivers may simply lackknowledge about the correct amount oflubricant to add and the adverse effects ofusing too much. Others believe that addingextra lubricant increases fuel economy andprovides greater protection against pistonseizure. To the extent that straight mineral oilmay not mix with gasoline as well as 2T oil, agreater quantity of lubricant is needed forlubrication. In reality this practice provideslittle or no benefit to drivers, but significantlyincreases the level of emissions and reduces thequality of air for society at large.

Finally, drivers are encouraged to buy toomuch lubricant by the filling station operatorsthemselves, who earn higher margins on oil thanon petrol. Furthermore, adulteration of gasolinewith kerosene is widespread in some countries inSouth Asia because of the large difference in theretail price of the two fuels. This practice increasesemissions because kerosene has a higher boilingpoint than gasoline and is therefore more difficultto burn. As a result more deposits build up in theengine and damage the engine over time, andmore unburned hydrocarbons are emitted in theexhaust gas.

Reducing Emissions from Two-StrokeEngines

Emissions from the existing fleet of two-strokegasoline engines can be reduced by (a) ensuringthat drivers use the correct type and quantity oflubricant, (b) improving vehicle maintenance, and(c) improving the quality of gasoline. For newvehicles, emissions can be reduced by (d) redesign-ing two-stroke engines to decrease scavenginglosses and the amount of lubricant needed, and(e) installing catalytic converters to further reducetailpipe emissions. Some of these measures can beachieved through regulation. Others require masseducation of drivers, vehicle owners, regulators,and even the public, which has a role in bringingpolitical pressure to bear on the problem.

Measures targeted at the existing fleet of two-stroke vehicles

Ensuring that drivers use the correct type and quantityof lubricant. In much of South Asia very fewdrivers of commercial three-wheelers use 2T oil.In Bangladesh the use of excessive amounts ofstraight mineral oil is the norm rather than theexception among three-wheeler drivers. The saleof straight mineral oil for use in vehicles is notillegal. Changing the behavior of these drivers touse the correct quantity of 2T oil, as well asraising the standards for the type of lubricant thatmust be used, would make an enormous differ-ence in particulate emission levels. Preliminarytests show that reductions of particulate matteremissions of as much as two-thirds may be

3Executive Summary

achieved through the use of the proper amountsof higher quality lubricants.3

At the technical level, metering the correctamount of lubricant directly into gasoline at thepump (the so-called premix in India) is one wayof ensuring that the correct type and quantity oflubricant is used. Banning the sale of “loose” oil infavor of the sale of premeasured sealed packetswould also help enforce adding the right amountat the petrol pump. The use of higher-quality 2T oilrepresents cost savings to most two-stroke vehicledrivers. Even though the oil itself is more expen-sive, analysis has repeatedly shown that 2T oilused in the proper amount costs less than driverscurrently pay for larger amounts of lower-gradeoils. In addition come nonquantified benefits oflonger engine life and lower emissions.

Improving vehicle maintenance. The importanceof an effective inspection and maintenanceprogram cannot be overemphasized: propermaintenance is critical to both increasing fuelefficiency and reaping the full benefits of emissionreduction investments. Simple servicing proce-dures—cleaning and adjusting the carburetor,adjusting the ignition system, cleaning andadjusting or replacing spark plugs, and cleaningair filters—can reduce exhaust emission levelssignificantly as well as improve fuel efficiency.Tying the frequency of inspection to the age of thevehicle and the annual number of kilometerstraveled could also increase the effectiveness ofinspection programs.

Improving the quality of gasoline. Eliminating thewidespread practice of adulterating gasoline withkerosene would reduce emissions. Reducing thegum content and increasing the octane level ofgasoline that does not meet the minimum speci-fied by vehicle manufacturers could also cutemissions. High gum content can cause an engineto misfire, damaging the vehicle and significantlyincreasing emissions of hydrocarbons and particu-late matter. Low octane can cause knocking andengine malfunction.

Measures targeted at the environmentalperformance of new two-stroke vehicles

Reducing scavenging losses. Substantial reductionsin scavenging losses have been achieved by

designing better port configurations. In India, forexample, short-circuiting fuel losses have beenreduced from 35 to 14 percent as a result of betterengine designs. Several new technologies forreducing scavenging losses are also being tested,but all of these would require an electronic enginemanagement system. While this system wouldadd to the cost of the vehicle, this cost would bepartially offset by improved fuel efficiency.

Installing catalytic converters. Installation ofcatalytic converters in two- and three-wheelerswould reduce exhaust emissions by about half.Vehicles with catalytic converters must use lead-free gasoline, however, which is not widelyavailable in some parts of South Asia. The dura-bility of catalytic converters for two-strokeengines is also an issue. For commercial three-wheelers catalysts are likely to have to be replacedat intervals ranging from six months to a year tomaintain reasonable emission levels. Whileessentially no data are available to quantify theimpact of catalytic converters on reducing par-ticulate emissions from two-stroke engines,estimates indicate that cost-effectiveness may bequestionable.

Replacing Two-Stroke Gasoline Engines

In addition to reducing emissions from two-strokegasoline engines, both governments and vehiclemanufacturers are finding cleaner alternatives tothese engines. Options include four-stroke gaso-line engines and engines powered by liquefiedpetroleum gas, compressed natural gas, andelectricity. As cleaner vehicles come on themarket, the share of the older, more pollutingvehicles will fall. In addition, retrofit kits that takeadvantage of cleaner fuels and lubricants arebecoming increasingly available for installation onolder two-stroke engine vehicles.

Four-stroke engines

Replacing two-stroke engines with four-strokeengines (at the time of vehicle replacement)would significantly reduce hydrocarbon andparticulate emissions, although emissions ofnitrogen oxides would increase.

The cost difference between new two- andfour-stroke engines is less than 10 percent. If


operating and maintenance costs are taken intoaccount—especially the 10–20 percent improvedfuel efficiency over the life of the vehicle—owninga four-stroke engine vehicle may be more economicalthan owning a two-stroke engine vehicle. If the socialbenefits of reduced emissions are factored in, thenet economic benefits are even higher. Thenegative socioeconomic effects of banning newtwo-stroke engines are small.

Vehicles powered by liquefied petroleum gas

Two-stroke engines powered by liquefied petro-leum gas (LPG) typically produce lower levels ofparticulate emissions than two-stroke gasolineengines. Moreover, since lubricant cannot bepremixed with LPG, it must be mechanicallymetered, eliminating the possibility ofoverlubrication. The main problems in introduc-ing LPG into the transport sector in South Asia arethe lack of sufficient domestic sources of supplyand the inadequate distribution system. India,Pakistan, and Sri Lanka import about 30–40percent of their LPG consumption. None of thecountries in the region has made the necessaryinvestments in LPG refueling stations, the lack ofwhich constrains widespread LPG use. In fact, theuse of LPG in vehicles is illegal in India and SriLanka today, although this situation is expected tochange in the near future.

Vehicles powered by compressed natural gas

Compressed natural gas (CNG) is a potentiallyattractive fuel because it emits little particulatematter, volatile organic compounds, or sulfuroxides when burned. Bangladesh and Pakistan arepiloting the use of CNG. Bajaj Auto in India hasdeveloped CNG-powered three-wheelers basedon a four-stroke engine design and began tomarket these in 2000.

Although replacing two-stroke gasolineengines with vehicles powered by CNG wouldreduce emissions, providing substantial subsidiesto promote such vehicles is not recommended. AsNew Zealand’s unsuccessful promotion programshows,4 adoption of CNG as an alternative fuelmust be based on economic viability, not artificialinducements. The economic viability of CNG-

powered vehicles depends on the local retail priceof natural gas. Switching to natural gas wouldmake economic sense only if the retail price ofCNG were about 55–65 percent of the cost of thefuel being replaced. Without consistently lowergas prices, promotion of CNG-powered vehiclesmay not be sustainable.

Governments have a disincentive to reduce theprice of CNG, however, since a consumer shiftfrom (taxed) fuels to (essentially untaxed) CNGwould reduce their tax revenues. In countriessuch as India that will soon begin importingliquefied natural gas on a large scale as a futuresource of natural gas, world crude prices couldmake it difficult to keep CNG prices much lowerthan gasoline prices. Bangladesh, however, withits large natural gas reserves and extensivenetworks of gas pipelines in large cities, might beable to introduce CNG into the transport sectorwithout compromising other needs in theeconomy.

Electric vehicles

Electric three-wheel vehicles are estimated to costnearly twice as much as gasoline-powered ve-hicles (based on market prices in India), haveshorter ranges, and run on batteries that take upto 6–10 hours to recharge. Until technologicalchanges make these vehicles more attractive, theyare not expected to play an important role inSouth Asia except in extremely polluted trafficcorridors. In Kathmandu, Nepal, for example,large electric three-wheelers known as Temposhave proved very popular with the governmentand passengers. In early 2000 about 500 of thesevehicles were operating in Kathmandu, partly inresponse to the ban on diesel Tempos imposed bythe government in 1999.

Standards and Enforcement

Emission-based standards tend to be more cost-effective than policies that dictate specifictechnologies. But enforcing emission standardsrequires effective inspection and maintenanceprograms. Policymakers can deal with pollutionby setting emission targets that vehicles mustmeet or by mandating specific types of fuel orvehicle technology in the hope of achieving

5Executive Summary

emission targets. Emission-based measuresprovide greater flexibility to suppliers of fuels andvehicles, who can choose the lowest-cost optionsfor meeting the specified emission targets. Pro-vided people comply with emission-basedstandards—and unfortunately their monitoringmay be more difficult than that of technology-based measures—they generally represent alower-cost option for society as a whole.

Regulations based on fuel and vehicle tech-nologies mandate the minimum technology toadopt. Such measures include banning two-strokeengines, mandating the use of catalytic converters,and requiring that a percentage of vehicles run ongaseous fuels. This approach is not likely to be alow-cost solution unless rigorous cost-benefitanalysis is performed to identify the optimaltechnologies for each specific situation.

At the heart of the policy debate concerningcontrolling emissions from new two- and three-wheelers is the level of emission limits, becausethe emission standards in turn may dictate thechoice of vehicle technology and even fuels.Taiwan (China) will effectively ban new two-stroke engine motorcycles in 2003 by makingemission standards so tight that only four-strokeengine motorcycles can meet them.5 The emissionstandards that came into effect in 2000 in Indiacan be met by two-stroke engine vehicles only ifoxidation catalysts are installed. The result is anincreasing move toward four-stroke engine two-and three-wheelers, although for very smallengines (for example, 50 cubic centimeters), two-stroke engines will remain the technology ofchoice in the foreseeable future.

Banning all two-stroke engines is not the answer.Banning all existing two-stroke engines in urbanareas would reduce emissions but eliminate point-to-point transportation for millions of SouthAsians. Women and families, who depend on thevehicles more than other groups, and the manypeople who use the vehicles commercially wouldbe particularly hard hit by a ban. Taking two-stroke three-wheelers off the road in a precipitousmanner would also affect the livelihoods of tensof thousands of drivers and invite widespread

agitation. Moreover, banning existing two-strokeengines without putting in place a well-docu-mented vehicle registration system, an effectivetraffic police force, and transport alternatives forthe current users could lead to increased harass-ment of drivers and corruption by traffic police.

More viable options are to: (a) ban older (andtypically more polluting) two-stroke vehicles fromurban areas; (b) raise annual registration fees forolder vehicles to incorporate environment-relatedfactors as well as vehicle book value; and/or (c)ban new two-stroke engine vehicles. The first twoapproaches seek to encourage the removal ofolder and more polluting vehicles from pollutedcities, either through their being scrapped orrelocated to less populated areas.

These options are best pursued if the followingconditions are met: (i) alternatives to the vehiclesbeing removed are readily available and market-tested; (ii) these alternatives are affordable, whichmay require the lowering or elimination of importduties or other taxes on new vehicles; and (iii)sufficient credit exists for vehicle owners anddrivers to be able to finance the purchase of thenewer vehicles. In assessing each of these mea-sures, policymakers need to weigh thesocioeconomic cost of making it more expensiveto own old vehicles against the public healthbenefits of reducing vehicular emissions.

In sum, two immediate simple solutions couldsignificantly improve air quality. Using the correcttype and concentration of lubricant and carryingout regular maintenance would significantlyreduce emissions from two-stroke engines whilepotentially saving drivers money. Promoting these“win-win” measures requires building publicawareness by disseminating information on thehealth impact of emissions; the types of engines,fuel, and lubricant that reduce emissions; theimportance of regular maintenance; and theadvantages and disadvantages of various mea-sures to mitigate air pollution. In South Asiapartnerships among government, industry, andthe public will continue to be crucial to bringingabout the changes required to achieve air qualitygoals.

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Air quality is deteriorating in the cities ofSouth Asia and is a byproduct of rapidurban population growth. Of the 1.3

billion people living in Bangladesh, Bhutan, India,Nepal, Pakistan, and Sri Lanka in 1998, 350million—27 percent of the combined populationof these countries—lived in urban areas. Theaverage population growth in urban centers, 3.2percent a year between 1990 and 1998, was muchhigher than the 1.3 percent rate of growth for thepopulation as whole.

A major source of air pollution is emissionsfrom the rapidly rising number of vehicles. In

India the number of registered vehicles tripled in10 years from 10.6 million in 1986 to 33.6 millionin 1996, an annual average rate of growth of morethan 12 percent (figure 1). The number of vehiclesgrew rapidly in other countries in the region aswell, increasing at an annual rate of 8.2 percent inBangladesh (1990–96), 13.5 percent in Nepal(1990–99), 8.0 percent in Pakistan (1990–99), and7.3 percent in Sri Lanka (1990–97). In the absenceof cleaner technologies and stringent controlmeasures, the level of vehicular emissions isexpected to increase at similarly high rates.

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The Role of Two- and Three-WheelVehicles in South Asia

Two-stroke engine vehicles in South Asia fall intotwo categories, two-wheelers and three-wheelers.Two-wheelers include mopeds, scooters, andmotorcycles and are used mostly for personaltransportation. Three-wheelers include small taxissuch as autorickshaws and larger vehicles such asTempos in Bangladesh and Nepal, which carry asmany as a dozen passengers.

Two- and three-wheelers play an importantrole in the transport market in South Asia. Indiahas a very large number of two-wheelers, whichare used for personal transport. Three-wheelers(called baby taxis in Bangladesh andautorickshaws in India and elsewhere) are typi-cally used as short-distance taxis. In Sri Lankasome families are buying three-wheelers forprivate use, attracted by the lower price of thevehicles relative to passenger cars.

Because they are used commercially, three-wheelers are driven much more thantwo-wheelers and require frequent maintenance.But drivers often fail to maintain their vehiclesproperly. The problem of maintenance is particu-larly severe when drivers lease their vehicles,because neither the driver nor the owner feelssolely responsible for the mechanical condition ofthe vehicle.

Three-wheel taxis are perceived as less compli-ant with traffic regulations and more accidentprone than four-wheel vehicles. They are alsomore visible, because of their numbers, andcontribute to congestion. For these reasons there isstrong sentiment in some countries, notablyBangladesh, against two-stroke engine three-wheelers.

Two-stroke gasoline engine vehicles areestimated to account for about 60 percent of thetotal vehicle fleet in South Asia (table 1). The large

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Vehicle type

Bangladesh

(1999)

India

(1997)

Nepal

(1999)

Pakistan

(1999)

Sri Lanka

(1997)

Cars 92,000 3,500,000 49,000 670,000 122,000

Taxis 2,300 420,000 — 68,000 6,000

Light-duty gasoline 52,000 740,000 2,600 310,000 14,000

Heavy-duty diesel 55,000 5,200,000 46,000 750,000 235,000a

Two -stroke three-

wheelers

68,000b 1,180,000 — 91,000 59,000

Four-stroke three-

wheelers

7,600b 210,000 5,900c — —

Two -stroke two-

wheelers

200,000d 21,800,000d 110,000d 1,700,000d 424,000d

Four-stroke two-

wheelers

35,000d 3,900,000d 19,000d 250,000d 75,000d

Total 523,000 37,200,000 232,000 4,000,000 936,000

Percentage of two-

stroke vehicles

51 62 47 45 52

9Understanding the Problem of Two-Stroke Engine Emissions

number of these vehicles, their age, poor mainte-nance, low lubricant quality and excessivelubricant use, and traffic congestion in large citiesmake two-stroke engine vehicles a significantsource of particulate emissions.

Two-stroke engines have several advantagesover four-stroke engines. These include lowercost; excellent torque and power; mechanicalsimplicity (fewer moving parts and resulting easeof maintenance); lighter and smaller engines;greater operating smoothness; and lower nitrogenoxide emissions. They also have disadvantagescompared with four-stroke gasoline enginevehicles, including higher particulate and hydro-carbon emissions, lower fuel economy, and loudernoise.6

Types of Emissions

Gasoline engines contribute to air pollution byemitting high levels of particulate matter (in thecase of two-stroke engines), lead if leaded gaso-line is used, carbon monoxide, nitrogen oxides,and volatile organic compounds. Diesel enginesemit high levels of particulate matter, nitrogenoxides, and sulfur oxides (if the level of sulfur indiesel is high).

The pollutant of special concern in South Asiais small particulate matter because of its highambient concentrations and documented impacton morbidity and premature mortality. The levelof particulate matter with an aerodynamic diam-eter of less than 10 microns (PM10) exceedsinternationally accepted standards by severaltimes in a number of cities in South Asia. Twomajor contributors to high ambient concentrationsof PM10 in the transport sector are two-strokeengine gasoline vehicles and heavy duty dieselvehicles.

Emissions are higher in two-stroke enginesbecause of the design of the engine. Gas is ex-changed through ports located in the cylinder,usually opposite each other. A fresh fuel and airmixture compressed in the crankcase entersthrough the intake opening, while exhaust gasesexit through the exhaust port. While both theintake and exhaust ports are open some of thefresh fuel and air mixture escapes through theexhaust port. As a result of these “scavenging

losses,” which can amount to 15–40 percent of theunburned fresh charge, the exhaust contains ahigh level of unburned fuel and lubricant (MECA1999). Nitrogen oxide emissions tend to be lowerbecause a significant portion of the combustionproducts remains in the cylinder.

In two-stroke engines the crankcase is not usedas an oil reservoir, as it is in four-stroke engines.Instead a small amount of lubricating oil is addedto the fuel or introduced continuously mechani-cally. Because lubrication is on a total loss(once-through) basis, incompletely combustedlubricant and other heavy hydrocarbons areemitted as small oil droplets. These oil dropletsincrease visible smoke and particulate emissions,with serious impact on public health because oftheir well-documented link to morbidity andpremature mortality (annex A).

Particulate emissions data from two-strokeengine vehicles in South Asia are scarce. Data onmotorcycles in the United States from the 1970smay be representative of pre-1991 two-strokeengine vehicles in South Asia (table 2). Morerecent data (table 3), from tests done in the fall of2000 at ARAI (the Automotive Research Associa-tion of India), indicate that particulate emissionslevels of in-use three-wheelers from Dhaka (enginesize of 150 cubic centimeters) are significantlyhigher than the data obtained in the 1970s. Thesetests also show that 7-year old vehicles usingexcess “straight mineral oil” emit particulatematter up to ten times, and that 4-year old ve-hicles using “straight mineral oil” emit particulatematter roughly two to three times, the typicalvalues obtained in the United States in the 1970s.For both ages of vehicles, particulate emissionsare much less if the correct amount of 2T oil,formulated specifically for use in two-strokeengine vehicles, is used.

Since two-stroke engine vehicles emit signifi-cantly more unburned gasoline than four-strokeengines, they emit more organic lead if leadedgasoline is used.7 Organic lead is much moredamaging to public health than inorganic leadformed by combustion of lead additives. Leademissions are a problem in countries such asPakistan that still sell only leaded gasoline.Fortunately, Bangladesh phased lead out ofgasoline in July 1999, India in February 2000, and


Pakistan and Sri Lanka are considering strategiesfor eliminating lead in gasoline.

Factors Exacerbating Emission

Poor vehicle maintenance, the misuse of lubricant,the adulteration of gasoline, and the lack ofcatalytic converters exacerbate two-stroke engineemissions. The age and poor maintenance ofmany two- and three-wheelers in the regionincrease emissions well above any applicablestandards. In addition, many drivers use lubri-cants and fuels of poor quality.

Misuse of lubricant

Both the quantity and quality of lubricant usedaffect the level of hydrocarbon and particulateemissions from two-stroke engines. Vehiclemanufacturers recommend adding 2 percent

lubricant for two-wheelers and 3 percent lubricantfor three-wheelers. But many drivers of three-wheelers add considerably more lubricant forseveral reasons:� Lack of knowledge about the correct amount to

add

� Lack of knowledge about the adverse effects ofexcess lubricant

� Addition of excess lubricant to gasoline byfilling station attendants at the point of sale

� Perception that more lubricant will providegreater protection against piston seizure

� Perception that more lubricant will increasefuel economy

� Lower miscibility of straight mineral oil andconventional motor oils with gasolinecompared to 2T oil.

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Model Type

Engine size

(cubic

centimeters) Hydrocarbons

Carbon

monoxide

Oxides of

nitrogen

Particulate

matter

Honda SL100a Four-stroke 100 1.3 13.7 0.21 0.02

Honda CL350K3a Four-stroke 350 2.5 28.9 0.03 0.03

Kawasaki 125F-6a Two -stroke 125 6.1 4.8 0.10 0.12

Suzuki T250a Two -stroke 250 12.9 21.6 0.02 0.35

Yamaha DT1-Ea Two -stroke 250 10.3 16.3 0.03 0.15

Kawasaki KE100b Two -stroke 100 5.6 20.5 — 0.34

Yamaha DT100 b Two -stroke 100 3.8 10.5 — 0.08

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VVehicle ageehicle age

LubricantLubricant

typetype

PPercentageercentage

lubricantlubricant HydrocarbonsHydrocarbons

CarbonCarbon

monoxidemonoxide

Oxides ofOxides of

nitrogennitrogen

PParticulatearticulate

mattermatter

7 years7 years straightstraight 8%8% 2323 2525 0.030.03 2.72.7

7 years7 yearsaa 2T2T 3%3% 1616 1717 0.090.09 0.90.9

4 years4 years straightstraight 8%8% 99 88 0.080.08 0.60.6

4 years4 years 2T2T 3%3% 99 1010 0.090.09 0.20.2

11Understanding the Problem of Two-Stroke Engine Emissions

Excessive use of lubricant increases combus-tion chamber deposits and fouls spark plugs.When pistons and rings are badly worn, excesslubricant may postpone piston seizure for a while.But the adverse social effects of much higheremissions far outweigh the benefits to vehicleowners.

Lubricant requirements for two-stroke enginesdiffer from those for four-stroke gasoline engines:good lubricity; piston cleanliness; low deposits,especially in the exhaust system; and low smokeemission. Two-stroke engine vehicles should usespecially formulated 2T oil. Becausepolyisobutene of moderate molecular weighttends to decompose without leaving heavydeposits, polyisobutene thickener in a base stockis increasingly used in lubricant. Japan has takenthe lead in developing new motorcycle oilsreferred to as low-smoke or smokeless lubricants.

Many three-wheelers in South Asia do not usethe 2T oil recommended by vehicle manufactur-ers. Instead they use straight mineral oil or new orrecycled engine oil, which results in greaterdeposit buildup and higher emissions (box 1). Theprincipal reason for using these oils is their lowercost, although some drivers may be under theimpression that these more viscous oils providegreater engine protection. In some countries, suchas Bangladesh and Sri Lanka, 2T oil is not readilyavailable at filling stations.

Conventional motor oils do not mix well withgasoline. Their use in two-stroke engine vehicles

results in insufficient lubrication when oil doesnot reach the engine and high emissions when itdoes. Long-term use of conventional lubricantsresults in premature wear of the engine andhigher maintenance costs.

Inadequate vehicle maintenance

Vehicular emissions are exacerbated by the age ofthe vehicle fleet and the poor state of vehiclemaintenance (ARAI, 1998). A study in the UnitedStates found that poorly maintained vehicles,which represented 20 percent of all vehicles on theroad, contributed about 80 percent of total vehicu-lar emissions (Auto/Oil Air Quality ImprovementResearch Program 1997). Recently three baby taxisin Dhaka, Bangladesh, from four to seven yearsold were randomly selected for mechanicalinspection. The engineers inspecting the enginesfound evidence of considerable ad hoc, unautho-rized repairs and modifications. A combination ofinadequate or improper maintenance and repairsby poorly trained mechanics contributes to thepoor mechanical state of many vehicles in SouthAsia .

Adulteration of gasoline

Emissions by all gasoline vehicles are exacerbatedby the adulteration of gasoline with kerosene.Kerosene has a higher boiling point than gasolineand is thus more difficult to burn. As a resultmore deposits build up in the engine and moreunburned hydrocarbons are emitted in theexhaust gas. Anecdotal evidence suggests thatadulteration of gasoline is widespread in SouthAsia because of the significantly lower retail priceof kerosene. Limited sampling and testing ofgasoline by the World Bank in Dhaka in 1998 alsoindicated that a significant fraction of gasolinehad been adulterated.

Lack of catalytic converters

Catalytic converters—installed in passenger carsin many parts of the world where unleadedgasoline is readily available—cannot be used toconvert a high proportion of hydrocarbons in two-stroke engines because current designs result ingreater exotherm (heat of reaction) and the

Box 1Reducing pollution while saving money

Many drivers in Bangladesh use mineral oil insteadof 2T oil because it is less expensive. But switchingto 2T oil would actually save most drivers money.Straight mineral oil in Dhaka sells for about 50 takasa liter, while 2T oil sells for about 90 takas a liter. Adriver of a baby taxi who uses 6 liters of gasoline aday and drives 280 days a year would typicallyspend 6,700 takas a year adding straight mineral oilat 8 percent concentration. A driver who switchedto a 3 percent concentration of 2T oil would spendjust 4,500 takas a year—an annual savings of 2,200takas. The switch to 2T oil would also reduce emis-sions and help maintain vehicles.

Source: Informal World Bank survey, 1999.


sintering of precious metals, which deactivates thecatalyst. The tendency of two-stroke engines tomisfire under low load conditions further aggra-vates the problem of catalyst deactivation. Despitethese limitations oxidation catalysts—which lowerthe emission levels of hydrocarbons and carbonmonoxide and to some extent reduce the amountof fine particles emitted in the form of oil drop-lets—have been used in Taiwan (China) to meetincreasingly tight emission standards. Beginningin 2000 these converters are installed in all newtwo-stroke engine two- and three-wheel vehiclesin India.

Health Impact of Emissions

Research in various cities and countries hasshown that PM10, and especially PM2.5 (particleswith diameters of no more than 2.5 microns,called fine particulate matter), are extremelydamaging to public health. These particles areassociated with respiratory symptoms, exacerba-tion of asthma, changes in lung function, andpremature death (Holgate and others 1999,chapter 13).

The health impact of particulate matterincreases as the size of the particle diminishes.Very fine particles—such as those emitted by thecombustion of transportation fuels—are believedto be particularly harmful. In addition, the factthat they are emitted near ground level, close towhere people live and work, suggests that vehicu-lar emissions are even more harmful than theirshare in total emission loads might indicate. (Adetailed discussion of the health impacts ofvarious pollutants is given in annex A.)

The health impact of oil droplet-based par-ticles is not well understood. Most health impactstudies have been carried out in countries that donot have large two-stroke engine vehicles, wherethe principal sources of fine particulate emissionsare diesel vehicles and stationary sources. In all ofthese studies, sickness and death are regressedagainst the overall ambient particulate concentra-tions measured in terms of total suspended

particles or PM10, not against vehicular particu-late emissions. Most of the particulate matter fromtwo-stroke engines is soluble organic matter,whereas particulate matter from diesel vehiclesand stationary sources contains a significantamount of graphitic carbon. Their behavior in theatmosphere in terms of nucleation, agglomeration,dispersion, and condensation could be quitedifferent. This area of research merits furtherinvestigation.

Effect of Emissions on Global Warming

Three greenhouse gases emitted by vehicles—carbon dioxide, methane, and nitrous oxide—arebelieved to have the potential to increase globalwarming. Two-stroke engines are not a majorsource of these emissions, however. The transportsector accounts for an estimated 13 percent ofcarbon dioxide emissions in South Asia, rangingfrom 10 percent in Bangladesh to 48 percent in SriLanka (International Energy Agency 1997).Emissions from two-stroke engine vehicles arerelatively low because of their low fuel consump-tion. Two-stroke engine vehicles account for about11 percent of vehicular carbon dioxide emissions(8 percent by two-wheelers and 3 percent bythree-wheelers) and a very small share of methaneand nitrous oxide emissions.

Only 1–2 percent of total greenhouse gases inSouth Asia can thus be tied to two-stroke enginevehicles. This very minor contribution of two-stroke engine vehicles to greenhouse gasemissions suggests that efforts to reduce suchemissions should target other types of vehicles,such as heavy-duty buses and trucks, and sectorsother than transport. Nevertheless, mitigationmeasures that reduce local pollution from two-stroke engines may lead to reduced greenhousegas emissions as well (see chapter 2). Examples ofsuch measures include switching to more fuel-efficient four-stroke engines and switching toelectric vehicles, especially where the electricityused to charge the vehicles is generated using aclean fuel such as natural gas.8

13

��

With the exception of India, countries inSouth Asia have not yet adoptedmeasures used in other parts of Asia

to mitigate emissions from two-stroke engines.These include use of low-smoke lubricants,installation of oxidation catalysts, and mechanicalmetering of lubricant. This section examines waysto improve the functioning of two-stroke engines.Chapter 3 looks at alternatives to two-strokegasoline engines.

Declines in Emissions

Emissions from recent two-stroke models havedecreased markedly as a result of technologicalimprovements. In Taiwan (China)—which has thelargest number of two-wheelers per capita in theworld—emission standards have tightenedsignificantly (table 4). The emission standards inTaiwan (China) also control visible smoke; smoke

opacity is limited to 15 percent for new vehiclesand 30 percent for in-use vehicles.

In India vehicle manufacturers faced thechallenge of meeting more stringent emissionstandards in 1996 without using catalytic convert-ers, which could not be used because unleadedgasoline was not widely available (table 5).Manufacturers had to rely solely on improve-ments in engine technology to meet the mandatedemission limits. Today as a result of continuingtechnological advances, including the installationof catalytic converters, new two- and three-wheelers manufactured in India emit less than 16percent of the carbon monoxide and less than 25percent of the hydrocarbons and nitrogen oxidesemitted by vehicles manufactured in 1991.

Emission factors of new and well-maintainedtwo-wheelers using the correct amount of lubri-cant have declined in recent years. A scooter

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YYearear Driving cycleDriving cycle

Catalyst durabilityCatalyst durability

requirementrequirement

(kilometers)(kilometers)

Carbon monoxideCarbon monoxide

(grams per kilometer)(grams per kilometer)

Hydrocarbons andHydrocarbons and

nitrogennitrogen oxidesoxides

(grams per kilometer)(grams per kilometer)

19881988 ECE 40ECE 40aa warmwarm NoneNone 8.88.8 5.55.5

19911991 ECE 40 warmECE 40 warm 6,0006,000 4.54.5 3.03.0

19981998 ECE 40 warmECE 40 warm 15,00015,000 3.53.5 2.02.0

20032003 ECE 40 coldECE 40 cold 15,00015,000 7.07.0 1.0/2.01.0/2.0bb


equipped with a catalyst, for example, emittedjust 0.015 grams of particulate matter per kilome-ter in a recent test (table 6), but even this emissionfactor is many times greater than that of a compa-rable four-stroke scooter.

But data on emission factors for particulatematter must be interpreted with caution. Noestablished methodology is accepted industry-wide for measuring particulate emissions fromtwo-stroke engines. Nearly all the work carriedout on two-stroke engine vehicles has focused onreducing hydrocarbons (or the sum of hydrocar-bons and nitrogen oxides), carbon monoxide, andvisible smoke. No in-depth study has beenconducted on particulate emissions.

Measurement of particulate matter emissionsfrom two-stroke engines is difficult because oildroplets from lubricant added to gasoline on apass-through basis account for a large fraction ofparticulate matter in the exhaust gas. Dependingon the dilution rate and the temperature to whichthe line downstream of the exhaust pipe (includ-ing the dilution tunnel) is heated, these dropletscan condense before being collected on filterpaper. Oil samples condensed on filter papers canalso be lost as a result of the passage of gasthrough the filter.

A reliable and reproducible methodology formeasuring particulate matter emissions from two-stroke engines should be developed andstatistically significant data collected to enhance

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Two-wheelers Three-wheelers

Year

Carbon

monoxide

Hydrocarbons and

nitrogen oxides

Carbon

monoxide

Hydrocarbons and

nitrogen oxides

1991 12–15a 8–9a, b 30 12b

1996 4.5 3.6 6.75 5.4

1998 4.5 3.6 6.75 5.4

2000 2.0 2.0 4.0 2.0

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Vehicle type

Odometer

(kilometers)

Amount of

lubricant Lubricant type

Particulate matter

emissions

(grams per kilometer)

Motorcyclea 215 Metering API TC/JASO FC* 0.055

Scootera 550 2% JASO FB 0.032

Scooter with catalysta 550 2% JASO FB 0.015

Scooter, four-strokea 650 n.a. n.a. 0.0005

Motorcycleb 19,000 Metering — 0.025

Motorcycleb 3,000 3% — 0.012

15Reducing Emissions from Two-Stroke Engine Vehicles

understanding of emissions from these vehiclesand help policymakers select optimal measuresfor curbing emissions. (Annex B presents theresults of recent tests of alternative hypothesesabout measurement problems.)

Improving Gasoline Quality

The adulteration of gasoline with kerosene islikely to increase hydrocarbon and particulateemissions. Because some of the gasoline effec-tively bypasses the combustion chamber and isemitted uncombusted by the two-stroke engine,eliminating or reducing such toxic components asorganic lead and benzene from gasoline—aworthwhile step under any circumstances—isparticularly important to mitigate the healthimpact of toxic emissions from two-stroke en-gines.

The high gum content and low octane level ofgasoline also increase emissions. If gasoline isunstable the gum content may become unaccept-ably high, leading to the deterioration ofcarburetor settings and increased deposits, whichalter the air-to-fuel ratio. This in turn could causethe engine to misfire, damaging the vehicle andsignificantly increasing emissions of hydrocarbonsand particulate matter comprising oil droplets.

While the minimum research octane number(RON)9 requirement for two- and three-wheelersin South Asia is 87, Bangladesh still markets 80octane gasoline widely. Depending on how thedriver accelerates, 80 RON gasoline can causeknocking and engine malfunction—and hencehigher emissions.

Improving Lubricant Use

Many drivers of two-stroke engine vehicles useexcessive quantities of the wrong kind of lubricant(see chapter 1). Correct use of lubricant can go farto reduce emissions from these vehicles.

Standards for lubricants

In the mid-1980s the American Petroleum Insti-tute (API) and the Coordinating EuropeanCouncil for the Development of PerformanceTests for Transportation Fuels, Lubricants, andOther Fluids set up a provisional two-strokelubricant performance and service classification

list. API canceled the system in 1993, deferring tothe International Organization for Standardization(ISO) global specification and the JapaneseStandards Organization (JASO) system. Oilmarketers continue to use the outdated testcriteria established for API TC to certify air-cooledoils. The API TC classification is currently thelowest acceptable level of 2T oil quality.

In 1990 JASO created a two-stroke lubricantstandard with three levels of quality (FA, FB, andFC). Lubricity and detergency quality increasefrom FA to FC, and exhaust blocking and smokeemission improve. Maximum permissible levelsof smoke density are 50 percent for FA oil, 44percent for FB oil, and 24 percent for FC oil.Japanese manufacturers of two-stroke vehiclesidentify FC (low-smoke lubricants) as theirminimum requirement. North America’s API TCoil rating is equivalent to JASO FB.

Since April 1999 the Government of India hasrequired all two-stroke engine oils sold in thecountry to meet both API TC and JASO FCspecifications (that is, only low-smoke lubricatingoils can be used in India). In the National CapitalTerritory of Delhi, 2T oil can be sold only in sealedpackages or premixed with gasoline and dis-pensed through the pump nozzle. This ban onunsealed packages is intended to discourage thesale of recycled and other unsuitable engine oils.The sale of premixed gasoline is intended toencourage the use of not only the suitable qualitybut also the correct amount of 2T oil.

Using the correct concentration of lubricant

The use of the correct amount of 2T oil signifi-cantly reduces two-stroke vehicular emissions.New lubricant formulations even allow certainmakes of two-wheelers to cut the lubricantrequirement to just 1 percent. Table 7 showsindicative emission factors as a function of theamount of lubricant and type for well-maintainedmotorcycles without any advanced emissioncontrol technologies. Particulate matter emissionfactors in the table are approximations based onlimited available data and indicative of generaltrends only. Since particulate emissions are notregulated in Asia, relatively little data areavailable.


Using low-smoke lubricant

The use of low-smoke lubricant significantlyreduces emissions of visible smoke. The retailprices of lubricants in India in March 2000 aregiven in table 8. If drivers using 6 percent JASOFB oil cut back the amount of lubricant to 3percent and simultaneously switch to JASO FC(low-smoke lubricant), they can realize savings ofabout 35 percent in lubricant costs.

In Bangkok, several motorcycles with varyinglevels of visible smoke emissions were selected tosee if visible smoke was correlated with massparticulate emissions. Some of the test results areshown in table 9. The mass particulate emissionsfor all the three driving cycles showed weakcorrelations with opacity for two-stroke enginevehicles using regular 2T oil. One four-strokeengine vehicle is included in the table to illustrateits low opacity as well as mass particulate emis-sions. Limited data on the impact of switchingfrom regular 2T oil to low-smoke lubricant onparticulate emissions indicate that while low-

smoke lubricant may reduce visible smoke, it maynot reduce mass particulate emissions (RadianInternational 1998 and unpublished data fromARAI). Thus the public health benefit of usinglow-smoke lubricant is not clear.

Metering lubricant

A mechanical lubrication system, which adjuststhe amount of lubricant metered into gasoline tothe engine speed and load, can control the amountof lubricant added to gasoline. Such a systemreduces emissions by making it impossible fordrivers to add excess lubricant to gasoline.However, mechanical lubrication may not yieldany greater benefits than drivers adding thecorrect amount of lubricant.

Improving Vehicle Design

In response to national standards more stringentthan those of the European Union (see box 2),Indian vehicle manufacturers have made enginedesign changes that have reduced the level of

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Particulate matter emissions Hydrocarbon emissions

Lubricant content

Grams per

kilometer

Percent

reduction

Grams per

kilometer

Percent

reduction

6–8%, regular 2T 0.6–0.7 n.a. 8.5 n.a.

5% maximum, regular 2T 0.35 50 7.0 18

2–3%, regular 2T 0.25 64 6.5 24

1–2%, regular 2T 0.20 71 6.0 29

1% maximum, low-smoke 0.15 79 5.7 33

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Lubricant

Price of

lubricant

per liter

Price of 3 percent

oil per liter of

gasoline

Price of 6 percent

oil per liter of

gasoline

Two -stroke oil meeting JASO FB

standard

80–90 2.4–2.7 4.8–5.4

Two -stroke oil meeting API TC and

JASO FC standards

100–120 3.0–3.6 6.0–7.2

Crankcase oil meeting API standard

SCa

80–90 2.4–2.7 4.8–5.4

17Reducing Emissions from Two-Stroke Engine Vehicles

0

2

4

6

8

10

12

14

0 1 2 3 4 5

Hydrocarbon emissions and nitrogen oxides (grams per kilometer)

Ca

rbo

nm

on

ox

ide

(gra

ms

pe

rk

ilo

me

ter)

EU 4 stroke

EU 2 stroke

Japan

4 stroke

Ja

pa

n

2str

oke

Taiwan (China)

India

emissions and increased fuel economy. Scaveng-ing losses have been reduced steadily, and in 2000catalytic converters were installed for the firsttime.

Installing catalytic converters

Catalytic converters for two- and three-wheelersare oxidation catalysts, which reduce the level of

carbon monoxide and hydrocarbon emissions butnot nitrogen oxides, rather than three-way cata-lysts commonly installed in passenger cars, whichalso reduce nitrogen oxide emissions. Catalyticconverters for two-stroke engines are not de-signed to achieve as high a level of conversion ofcarbon monoxide and hydrocarbons as those forfour-stroke engine passenger cars because of the

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Driving cycle

Type

Opacity

(percent) ECE 40 FTP 75 Bangkok

Four-stroke 7 0.01 0.12 0.02

Two -stroke 20 0.26 0.26 0.04

Two -stroke 54 0.29 0.22 0.22

Two -stroke 77 0.19 0.18 0.13

Two -stroke 86 0.47 0.70 0.29

Two -stroke 100 0.41 0.23 0.14

Box 2Emission standards from around the world

The emission standards for two-wheelers differ markedly. The emission standards in India and Taiwan (China)today rank among the most stringent in the world, reflecting the concern of the authorities with controllingemissions from vehicles that are numerous and popular because of their affordability and ease of maneuver. Theemission standards shown below came into force in 2000, with the exception of those for Taiwan (China), whichcame into effect in 1998.


greater quantity of hydrocarbons and lubricant inthe exhaust gas. They typically reduce exhaustemissions by half.

Catalysts deactivate more rapidly in two-stroke engine vehicles, partly because of higherexhaust gas temperature, and need to be replacedfrequently. India is considering minimum catalystdurability requirements. Taiwan (China) has hadcatalyst durability requirements for motorcyclesfor some time, initially set at 6,000 kilometers andat 15,000 kilometers today. For three-wheelers inSouth Asia, which are often driven 120 kilometersa day, 15,000 kilometers is equivalent to less thansix months of operation. For a vehicle driven 10years or more, as many two-stroke vehicles inSouth Asia are, the catalyst might have to bereplaced up to 20 times to maintain the originallevel of particulate emissions. This is clearly aproblem.

In India the Society of Indian AutomobileManufacturers (SIAM) is offering the governmenta warranty of 30,000 kilometers for all two- andthree-wheelers equipped with catalytic convert-ers. Catalyst durability of 30,000 kilometerswould enable drivers to replace their catalysts atthe same intervals as they have their enginesoverhauled.

To meet year 2000 emission standards, thethree-wheelers manufactured in India areequipped with catalytic converters for both two-stroke and four-stroke engine designs. Thenet-of-tax cost of the catalytic converter fitted inthree-wheelers for both engines is approximately1,100 Indian rupees, or US$25.

Reducing scavenging losses

A major area of research and development hasbeen the attempt to reduce scavenging losses toincrease fuel economy and reduce emissions (box3). Substantial reductions have been achieved bydesigning better port configurations. In India, forexample, short-circuiting fuel losses have beenreduced from 35 percent in 1991 to as low as 14percent in the year 2000 model as a result ofdesign changes (Iyer 1999).

Improving Maintenance

The importance of an effective inspection andmaintenance program cannot be overemphasized:

proper maintenance is critical to reaping the fullbenefits of investments in emission mitigation.Simple servicing procedures, such as cleaning andadjusting the carburetor, adjusting the ignitionsystem, cleaning and adjusting or replacing sparkplugs, and cleaning air filters, can reduce exhaustemission levels significantly (ARAI 1998). Airfilters should be cleaned or replaced every 3,000kilometers. Carburetors should be tuned andcleaned every 3,000 kilometers for two-strokeengines and every 5,000 kilometers for four-strokeengines.

Because lubricant passes through the two-stroke engine on a once-through basis, there isconsiderably more deposition and accumulationof carbonaceous deposits in the combustionchamber, exhaust port, and silencer than in four-stroke engine vehicles. As a result more frequentdecarbonization is needed. Bajaj Auto recom-mends decarbonization every 6,000 kilometers forthree-wheelers and 9,000 kilometers for scooters.Four-stroke engines do not normally need decar-bonization. Bajaj also recommends replacingspark plugs every 7,500 kilometers for two-strokeengines and every 10,000 kilometers for four-stroke engines. Decarbonization requires mainlylabor, which is relatively cheap in South Asia,keeping maintenance costs low.

It is not clear whether long-run maintenancecosts are higher for two-stroke or four-strokeengines. Four-stroke engines have many moremoving parts (valves, camshafts, timing chains,oil pumps), which are relatively expensivebecause they tend to be sold by vehicle manufac-turers. In contrast, parts for two-stroke enginesare sold by a large number of parts suppliers.Labor costs for servicing four-stroke engines arealso higher because of the higher level of skillsrequired. Engine overhauls for two-stroke enginesare more expensive, however. Minor engineoverhauls, not normally required on four-strokeengines, are typically required every 30,000kilometers for two-stoke engines. Major over-hauls, which may also be needed on four-strokeengines, are required every 90,000 kilometers fortwo-stroke engine three-wheelers.

19

Box 3Reducing scavenging losses in two-stroke engines

Several technologies are being tested to reduce emissions from two-stroke engines (see table below). The goal isto retain the advantages of the two-stroke engine while gaining control over the air-to-fuel ratio and eliminatingthe loss of air-fuel mixture through the exhaust port.

Injecting fuel into the engine instead of introducing it through the carburetor may dramatically reduce oreliminate scavenging losses. Direct injection of the fuel into the engine also makes it possible to use leaner air-fuel mixtures through charge stratification.

The effectiveness of a variety of systems that could be suitable for small engines has been demonstrated inlaboratories, although none has yet been developed commercially. The technologies being tested include:� Spraying pressurized fuel into the intake port or crankcase with controlled injection timing.� Injecting a fuel spray into the transfer port or the piston.� Injecting fuel into the cylinder as or after the exhaust port closes.� Directing the in-cylinder injection toward the cylinder wall to improve fuel atomization, vaporization, and

mixing.� Using “skip firing” along with fuel injection to shut off fuel injection in some cycles to allow sufficient time for

the exhaust gases to be purged from the combustion chamber.All of these measures would require an electronic engine management system for precise control of the fuel

injection timing and quantity, depending on the engine load and speed. They would thus add to the cost of thevehicle.

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Technology Hydrocarbons Carbon monoxide

Oxides of

nitrogen

Carburetor system 3.8 3.7 0.03

Cylinder wall injector 2.9 3.4 0.06

Semidirect injection 0.8 0.8 0.1

Electromechanical direct injection 0.8 0.8 0.1

Loop-scavenged two-stroke engine with air-

assisted direct injection

0.5 0.4 0.05

Air-assisted cylinder head injector with skip

injection and catalytic converter

0.28 0.09 0.16

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21

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Vehicle and fuel alternatives to two-strokegasoline engines can reduce exhaustemissions. Cleaner alternatives include

four-stroke engines and engines powered byliquefied petroleum gas, compressed natural gas,and electricity.

Four-Stroke Gasoline Engines

If gasoline is retained as the fuel of choice, replac-ing two-stroke vehicles with four-stroke vehicleswould significantly reduce hydrocarbon andparticulate emissions. Emissions of nitrogen oxidewould increase, however.

Because there are no scavenging losses in four-stroke engines, a much larger percentage of thefuel is combusted in the combustion chamber,

resulting in 10–20 percent greater fuel efficiency(table 10). Savings from better fuel economywould easily offset the higher purchase price offour-stroke engine vehicles, making this a poten-tially strongly cost-effective way to reducepollution.

Four-stroke engine two-wheelers have been onthe market for some time. All motorcycles sold inthe United States are of four-stroke design.Mishuk in Bangladesh has been selling four-strokeengine three-wheelers for a number of years.Four-stroke engine three-wheelers were notavailable in India until mid-2000, when Bajaj Autobegan marketing them there. Year 2000 modelthree-wheelers are equipped with catalyticconverters for both two-stroke and four-stroke

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Vehicle type Engine type Model year

Engine size

(cubic

centimeters)

Laboratory test

fuel economy

(kilometers per liter)

On-road fuel

economy

(kilometers

per liter)

Scooter Two -stroke Post-1996 150 55 52

Scooter Four-stroke Post-1996 150 62 59

Three-

wheeler

Two -stroke Pre-1996 150 24 20

Three-

wheeler

Two -stroke Post-1996 150 28 25–27

Three-

wheeler

Four-stroke 2000 175 33 30–31


engines. The ex-Delhi showroom prices areRs.66,579 for two-stroke and Rs.70,463 for four-stroke engine three-wheelers, with a pricedifference of Rs.3,884 (US$88). This incrementalcost is easily recovered in fuel savings in less thana year by operators of four-stroke engineautorickshaws (see chapter 4).

Diesel three-wheelers have even higher fuelefficiency than four-stroke engine vehicles.Moreover, because they are based on a four-strokeengine design, lubricant does not need to beadded to the fuel. Diesel three-wheelers are alsomanufactured to meet particulate matter emissionstandards. However, diesel exhaust has recentlybeen found to be more toxic than previouslybelieved. And diesel three-wheelers are consider-ably noisier than gasoline three-wheelers. Dieselengines are thus probably not a good alternativeto gasoline-powered two-stroke engines.

Vehicles Powered by LiquefiedPetroleum Gas

Liquefied petroleum gas (LPG) is a mixture oflight hydrocarbons, mainly propane/ propeneand butane/butenes. It is easier to distribute andstore than compressed natural gas, liquefied atpressures of 4–15 bar.

LPG is a much cleaner automotive fuel thangasoline. If LPG (or CNG) vehicles are based on atwo-stroke engine design, lubricant will still needto be metered and injected into the combustionchamber, thereby partially offsetting the emissionreductions achieved as a result of replacinggasoline with a gaseous fuel. Since lubricantcannot be premixed with LPG, it is metered intothe vehicle engine, eliminating the possibility ofoverlubrication. LPG also contains fewer highlyreactive hydrocarbons and has a lower sulfurcontent than gasoline or diesel fuel. LPG doescontains light olefins, highly reactive hydrocar-bons that increase emissions and lower theknock-limited compression ratio, diminishingengine performance.

LPG three-wheelers are used widely in Thai-land. Fueling vehicles with LPG is illegal in India,although this situation is likely to change in thenear future. Three-wheelers have been illegallyconverted to LPG use in Bangalore. ARAI and

Shakti Gas have jointly developed a conversionkit to run three-wheelers on LPG.

While not as good as CNG, LPG has superiorantiknock characteristics compared to gasoline.Propane has an antiknock index (the average ofresearch and motor octane numbers10) of 104,allowing LPG-powered engines to operate atslightly higher compression ratios than gasoline-powered vehicles. In India vehicle manufacturershave proposed a minimal motor octane numberfor automotive LPG of 89 to ensure that about 90percent of LPG is propane.

The main problems in introducing LPG intothe transport sector in South Asia are the lack ofsufficient domestic sources of supply and theinadequate distribution system. India, Pakistan,and Sri Lanka import about 30–40 percent of LPGconsumption. There is also a need to invest inrefueling equipment required to transfer pressur-ized LPG from storage tanks to vehicles and toensure that no LPG escapes during refueling. Thelack of adequate investment in LPG refuelingstations constrains widespread use of LPG inSouth Asia.

Vehicles Powered by CompressedNatural Gas

Switching to CNG reduces particulate matter andhydrocarbon emissions significantly. The combus-tion of CNG also yields essentially no volatileorganic compounds or sulfur oxide emissions.Moreover, because natural gas is lighter than air,on escape it will not lie on the ground or entersewage systems. CNG is expensive to distributeand store, however, requiring compression toabout 200 bar.

Both Bangladesh and Pakistan are piloting theuse of CNG vehicles. In Bangladesh a pilotprogram funded by the Canadian InternationalDevelopment Agency converted four three-wheelers in mid-2000; a larger demonstrationinvolving 20–50 vehicles will follow. In Pakistan adonor-funded program plans to test 10–30 ve-hicles in Karachi, Lahore, and Quetta. In bothprograms one tank of CNG is estimated to have arange of about 100 kilometers. Bajaj Auto in Indiahas developed CNG-powered three-wheelersbased on a four-stroke engine design, which itlaunched in mid-2000.

23Alternatives to Two-Stroke Gasoline Engines

Vehicles can be produced to run on either CNGor gasoline. Such vehicles make less efficient useof CNG, however, losing about 10–15 percent oftheir power output. Efficiency is also lost as aresult of the extra weight of carrying two fuelsystems.

Methane, which constitutes the bulk of CNG,has an antiknock index of more than 120. Vehiclesthat run on CNG can thus take advantage of thehigh octane number of the fuel and operate at ahigh compression ratio. In practice the composi-tion of pipeline natural gas varies, depending onthe source and processing of the gas as well as thetime of the year. As a result, not only does the fueloctane number vary but the heating value canvary by as much as 25 percent, affecting vehicleperformance. Moreover, when used as fuel invehicles, the heavier hydrocarbons in natural gascan condense and revaporize, affecting the levelof fuel enrichment. Changes in fuel enrichmentaffect both emissions and engine performance.The water content of natural gas is also a concernbecause of its tendency to form solid hydrates andcorrode transmission pipes, vehicle storage tanks,and refueling stations.

The long-term viability of CNG vehiclesdepends on a favorable legislative and regulatoryatmosphere and fuel prices that are not distortedby subsidies. Efforts to encourage the purchase ofCNG vehicles through subsidization are unsus-tainable—as New Zealand’s failed attempt tojumpstart the conversion to CNG illustrates. NewZealand’s aggressive program of financial incen-tives, including subsidies, led to the conversion of110,000 vehicles to natural gas between the early1980s and 1986. When the government withdrewits support, however, the market for CNG vehiclesessentially died: today only about 10,000 suchvehicles remain on the road. As the InternationalAssociation for Natural Gas Vehicles put it,“Governments that believe that all they need is atwo- to three-year kick-start are wasting their timeand money” (Cumming 1997).

For converting to natural gas to make eco-nomic sense, the retail price of CNG needs to fallto about 55–65 percent of the cost of the fuel beingreplaced. Without consistently lower prices,promotion of CNG vehicles will not be sustain-

able. But governments have a disincentive toreduce the price of CNG since this would reducetheir tax revenues as consumers shift from (taxed)fuels to (essentially untaxed) CNG.

In countries such as India that will soon startimporting liquefied natural gas on a large scale (asource of natural gas in the future), it would bedifficult to keep CNG prices much lower thangasoline prices if world crude oil prices were tofall markedly. In contrast, Bangladesh, which haslarge natural gas reserves and extensive networksof gas pipelines in large cities, might be able tointroduce CNG into the transport sector withoutcompromising other needs in the economy.However, natural gas is effectively subsidized inBangladesh. In 1998 the price of natural gas wasestimated to average about 25 percent less than itseconomic opportunity cost. Once the gas sector isrestructured to reflect market prices, the econom-ics of CNG vehicles will become less favorablethan they are today—something that must beconsidered in assessing a CNG vehicle program.

Electric Vehicles

Electric three-wheelers cost much more thangasoline-powered vehicles, have shorter ranges,and run on batteries that take up to 6–10 hours torecharge. Until technological changes make thesevehicles more attractive, they are not expected toplay an important role in South Asia.

Electric vehicles currently operate on lead acidbatteries.11 When the batteries are chargedindoors, good ventilation is necessary, becausehydrogen is emitted as lead acid batteries re-charge. Preliminary estimates in India price thebatteries at about $40–$50 apiece for three-wheelers that operate on eight batteries. The eightbatteries and required vehicle modifications areexpected to increase the cost of electric three-wheelers by about $1,000, effectively doubling theprice of the vehicles relative to gasoline-fueledthree-wheelers in India.

The economic viability of electric vehiclesdepends in part on the price of electricity. Thepower sector in South Asia is being reformed andrestructured. The long-term viability of electricvehicles should be evaluated based on marketpricing of electricity.


Given the current state of technology, electricvehicles are not expected to have widespreadapplications in South Asia. They could play auseful but limited role, however, in extremelypolluted traffic corridors. In Kathmandu, Nepal,for example, electric Tempos were introduced in1994 (box 4). In 1995 the government reducedimport duties on electric vehicle components from60 to 5 percent, and duties on fully assembledelectric vehicles from as much as 150 percent to 10

percent. In early 2000 about 500 electric Temposoperated in Kathmandu, partly in response to theban on diesel Tempos imposed by the governmentin 1999. Seven plants assembled more than 200electric Tempos in 1999. This is the world’s largestfleet of electric road public passenger transportvehicles. The future is not secure, however, as thegovernment approved in May 2000 the import of300 15-seat vans with the same preferential importduties accorded to the electric vehicles.

Box 4Converting diesel three-wheelers to electric Tempos in Kathmandu

An important mode of public transport in Kathmandu is the Tempo, a 10-passenger three-wheeler that operatesas a minibus. Before the government banned diesel Tempos in Kathmandu in 1999, about 1,500 of the vehiclesoperated in the city.

A pilot program to convert diesel Tempos to electricity was conducted in 1994–96 by Global Resources Insti-tute with the support of the U.S. Agency for International Development (Moulton and Cohen 1997). The electricTempos in the pilot program, called Safa (clean) Tempos, had an operating range of 50 kilometers and a maximumspeed of 45 kilometers an hour. Their batteries weighed 360 kilograms, so that when full the vehicle operatedclose to its maximum design load. The brakes also operated close to design limits.

To allow the vehicles to travel 150 kilometers a day, three sets of batteries were used. Specified stops loadingand unloading passengers—a new concept in Nepal—were established so that the vehicles could operate on aschedule.

The Safa Tempos are cleaner and quieter than diesel Tempos, and public acceptance of the vehicles has beenhigh. In fact, demand from passengers often exceeded available space during the pilot period.

25

��

Policymakers can deal with pollution bysetting emission targets that vehiclesmust meet or by mandating specific types

of fuel or vehicle technology in the hope ofachieving emission targets. Emission-basedmeasures provide greater flexibility to suppliersof fuels and vehicles, who can choose the lowest-cost options for meeting the specified emissiontargets. Provided that compliance can be ensured,this approach is generally a lower-cost option forsociety. However, emission-based measures areusually more difficult to monitor than technology-based options. Technology based options are notlikely to be a low-cost solution unless rigorouscost-benefit analysis is performed to identify theoptimal technologies for each specific situation.(For a brief discussion of available software forevaluating emission sources, see annex C.)

The distinction between emission-based andtechnology-based policies is not necessarily sharp,because vehicular emission standards can bemade so stringent that they effectively dictate thetype of vehicle or fuel that must be used. Anexample is the year 2003 emission standards inTaiwan (China), which set tighter emissionstandards for two-stroke engines than for four-stroke engines, effectively banning two-stroketwo-wheelers.

Emission-Based Policies

Emission-based policies set vehicular emissionstandards and allow the automobile and oil

industries to seek the lowest-cost means ofcomplying with the standards. Vehicle manufac-turers prefer emission-based policies, which allowthem to explore different technology options andselect technologies themselves on the basis ofmarket requirements and their research anddevelopment activities. Emission-based policieswork well if the automobile and oil industriescooperate. Without cooperation, each industry hasan incentive to unload capital-intensive activitiesonto the other.

Stricter emission standards are apparentlypushing Indian manufacturers to build more four-stroke engine vehicles. Moving to a four-strokeengine appears to be cost-effective: anautorickshaw driven 120 kilometers a day 300days a year would save about Rs.7,200 a year(based on the prices of 87 octane gasoline andlubricant for two-stroke engine vehicles meetingJASO FC standards in mid-2000). Since the ex-Delhi showroom price difference between atwo-stroke and a four-stroke engine vehicle isRs.3,900, the incremental cost of purchasing afour-stroke engine three-wheeler is recovered in alittle over half a year. Assuming that maintenancecosts are comparable, replacing old autorickshawswith new four-stroke engine autorickshaws istherefore a cost-effective way of reducing fineparticulate emissions.

Monitoring emissions

While checking compliance of new vehicles maynot be difficult, monitoring the performance of in-

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use vehicles is a far greater challenge. At a mini-mum, an effective inspection and maintenanceprogram needs to be in place, together with anup-to-date vehicle registry. Even when imple-mented rigorously, however, inspection andmaintenance have limited effectiveness becauseowners and mechanics can temporarily adjustvehicles, particularly older technology vehicles, sothat they pass emissions tests.

One way to ensure that emissions consistentlymeet standards is to spot-check vehicles on theroad. However, such tests are expensive to set upand administer and invite corruption.

To increase the effectiveness of inspection andmaintenance programs, the frequency of inspec-tion could vary with the age of the vehicle as wellas the annual number of kilometers traveled.Commercial vehicles such as three-wheelers couldbe inspected more frequently than motorcyclesdriven for private use.

Frequent inspection is particularly importantonce oxidation catalysts are installed. If catalystslast about 30,000 kilometers and taxis are typicallydriven in two shifts for 150 kilometers a day,inspection and replacement of catalysts would benecessary twice a year.

Repairing vehicles that fail inspection

Vehicle inspection will be ineffective if vehiclesthat fail are not repaired promptly. The availabil-ity of adequately equipped and trained mechanicsis a prerequisite for a successful inspection andmaintenance program. Since four-stroke enginevehicles are more complex and require highermechanical sophistication to service, training ofmechanics should be given high priority in thecoming years. There is currently a shortage ofmechanics who can service four-stroke enginethree-wheelers and vehicles with increasinglysophisticated technology in general, and of repairshops with diagnostic tools to service suchvehicles.

Where vehicles are not driven by their owners,the incentives for regular inspection and mainte-nance, weak in the best of circumstances, are evenweaker, since the vehicle owner who is respon-sible for passing inspection does not have thevehicle most of the time. This dilemma highlights

the importance of finding ways to enforce emis-sion standards and deal with noncompliance,given that neither the owners nor the drivers havean incentive to spend time having commerciallyoperated vehicles inspected.

Technology-Specific Policies

Measures based on fuel and vehicle technologymandate the minimum technology to be adopted.Technology-specific policies include:� Mandating higher-quality two-stroke engine

lubricants

� Mandating premixing of gasoline and lubricant

� Mandating installation of catalytic converters

� Banning two-stroke engines

� Banning or providing incentives to scrapvehicles that have reached a certain age ornumber of kilometers traveled

� Mandating or providing incentives (tax credits,tax reduction, tax elimination, or subsidies) forreplacing two-stroke gasoline engine vehicleswith four-stroke engine vehicles

� Mandating or providing incentives forreplacing two-stroke gasoline engines withalternative fuels such as liquefied petroleumgas, compressed natural gas, and electricity.

Where emission-based policies are difficult tomonitor, it may make sense to adopt some ofthese policies. Before this is done, however, it isimperative that policymakers examine the cost-effectiveness of each option. Some measures makemore sense to mandate than others. Banning thesale of unpackaged lubricant would preventinferior quality lubricant from being added togasoline (box 5). Requiring that all new three-wheelers use four-stroke technology may bereasonable given the fuel cost savings, providedthat enough mechanics are trained to service four-stroke engine three-wheelers.

In contrast, the rationale for mandatingcatalytic converters is much weaker, since theycan function efficiently only if several conditionsare satisfied:� Unleaded gasoline must be widely available.

Ideally, leaded gasoline would be completelyphased out to eliminate the chances of fueling

27Policy Options

catalyst-equipped vehicles with leadedgasoline.

� Gasoline must have a reasonably low level ofsulfur, preferably less than 500 parts permillion by weight.

� Emission levels and the length of time thecatalyst system must meet those levels must bespecified.

� An effective inspection and maintenancesystem must be in place to ensure that catalyticconverters are replaced as needed.

If these conditions are not met, the benefits ofcatalytic converters may not justify the cost ofinstalling them. Even if these conditions are met, itstill makes sense to specify emission levels fornew vehicles rather than mandate catalyticconverters. Retrofitting in-use vehicles withcatalytic converters is problematic becausemisfires, which are more common in two-strokeengines, can cause temperature runaway andcatalyst sintering and damage the catalyst as aresult. For this reason Bajaj Auto in India recom-

mends that only two-stroke engine vehicles builtafter 1996 be considered for retrofitting.

Reducing particulate matter by mandatingcatalysts may not be cost-effective. It is difficult toestimate the impact of oxidation catalysts onparticulate matter emissions because data arescarce. Assuming catalyst conversion efficiency of50 percent, a particulate matter emission factorwithout catalysts of 0.1–0.2 grams per kilometer,and catalyst durability of 30,000 kilometers, thetotal amount of PM10 eliminated by the catalystwould be 1.5–3.0 kilograms. This translates toUS$8,000–17,000 per ton of PM10 given the net-of-tax catalytic converter cost of US$25 apiece in India.This figure varies severalfold depending on theassumptions made about the durability of thecatalyst and the amount of particulate matterreduced, but the cost figures remain on the high sidecompared with other PM10 reduction strategies.

Banning all two-stroke engines

Banning all two-stroke engines would eliminatepoint-to-point transportation for millions of South

Box 5The role of the supreme court in air quality management in Delhi

In July 1998 the Supreme Court of India mandated several measures affecting two- and three-wheelers in Delhi tocombat air pollution:1. Banning the sale of loose 2T oils at filling stations and service garages, effective December 1998.2. Mandating that filling stations mechanically meter lubricant to be mixed with gasoline at the point of gasoline

sale for two-stroke engine vehicles, effective December 1998.3. Mandating the replacement of all pre-1990 autos and taxis with new vehicles using clean fuels, effective March

2000.4. Introducing financial incentives for replacing all post-1990 automobiles and taxis with new vehicles using

clean fuels, effective March 2001.

The first three measures have been implemented. The third measure effectively requires that pre-1990autorickshaws be retired from Delhi and replaced with autorickshaws powered by compressed natural gas. Theonly two “clean” fuel options, until the use of liquefied petroleum gas is legalized in India, are natural gas andelectricity. No electric-powered autorickshaws are commercially available for sale in India today.

The fourth measure has had an interesting history. The Delhi government offered financial incentives untilMarch 2000 to replace autorickshaws 15 years old or older with new vehicles meeting the April 1996 emissionstandards. Although both two-stroke and four-stroke engines were permitted in principle, only two-stroke en-gine autorickshaws were available during this period. The incentive package consisted of complete exemptionfrom sales tax (6 percent until 2000, when it was raised to 12 percent) and subsidized loans from the DelhiFinance Corporation. The loan repayment period, ranging from three to five years, could be negotiated. As ofApril 2000, the financial package is offered only for the replacement of old autorickshaws with new autorickshawsrunning on compressed natural gas or electricity.

Autorickshaw owners’ response to the measures has been overwhelming. By March 2000 nearly 20,000 oldautorickshaws had been replaced by new ones. While the order allows owners to sell their old vehicles outsidethe National Capital Territory of Delhi, most owners chose to scrap their vehicles. Pollution is thus not trans-ferred to other parts of the country, and there is no possibility of these old vehicles migrating back to Delhi.


Asians and cause hardship until there are enoughbuses and four-stroke engine taxis to replace thelarge existing stock of two-stroke engine three-wheelers. Women and families, who depend onthe vehicles more than other groups, and themany people who use these vehicles commerciallywould be particularly hard hit by a ban. Takingtwo-stroke three-wheelers off the road precipi-tously would also affect the livelihoods of tens ofthousands of drivers and invite widespreadagitation. Moreover, banning existing two-strokeengines without putting in place a well-docu-mented vehicle registration system, an effectivetraffic police force, and transport alternatives forthe current users could lead to increased harass-ment of drivers and corruption by traffic police.Thus rather than banning these vehicles,policymakers should consider other lower-costoptions for reducing their emissions.

More selective bans

Lower cost and politically more viable options tobanning all two-stroke engine vehicles are to:(a) Ban only older (and typically more polluting)

two-stroke engine vehicles from urban areas.This approach has already been taken in Delhi,with widespread popular support (box 5);and/or

(b) Ban new two-stroke engine vehicles. This islikely to have less socioeconomic impact thanbanning all such vehicles, since the costdifference between new two- and four-strokeengines is not significant. If operating andmaintenance costs are taken into account,owning a four-stroke engine vehicle may bemore economical than owning a two-strokeengine vehicle. Removing financialdisincentives for replacing two-stroke enginethree-wheelers with four-stroke engine vehiclesis a high-priority.

Either of these two options would be bestpursued if the following conditions are met: (i)alternatives to the vehicles being removed arereadily available and market-tested; (ii) thesealternatives are affordable, which may require thelowering or elimination of import duties or othertaxes on new vehicles (see below); and (iii)

sufficient credit exists for vehicle owners anddrivers to be able to finance the purchase of thenewer vehicles.

Fiscal and Trade Policy Options

Whether or not the technology-specific measuresare adopted, economic policy options exist toencourage the removal of older and more pollut-ing vehicles from polluted cities. These optionsinclude providing tax incentives for renewingvehicles, offering cash for older vehicles to getthem off the road, ensuring credit for purchasingnew vehicles, and liberalizing the trade in newvehicles. Not all options are equally recom-mended.

Tax incentives for vehicle renewal

The structure of taxes and other vehicle charges,such as annual registration fees, should be care-fully reviewed and revised if necessary wheresuch structures do not capture the cost of pollu-tion. For example, the import tariffs or sales taxeson cleaner alternatives to autorickshaws (whethernew vehicles or parts for vehicle retrofitting)should not be so high as to discourage theirpurchase—since the public health benefits to begained are high. Similarly, annual registration feesbased solely on the market value of the vehicle,rather than on market value and pollution emit-ted, would be too low to discourage the use ofolder vehicles in urban areas. In assessing each ofthese measures, policymakers need to weigh thesocioeconomic cost of making it more expensiveto own old vehicles against the health benefits ofreducing vehicular emissions.

Offering cash payments for older vehicles to removethem from the road

Government purchase of older vehicles can distortthe market and have the perverse effect of keep-ing older vehicles in use. If the government offersto buy older vehicles, the price of those vehicles,many of which may be on the verge of beingscrapped, will rise. A vehicle is typically scrappedwhen the cost of repairing it exceeds the marketvalue of the vehicle after repair. The higher pricesof older vehicles may have the unwanted effect of

29Policy Options

inducing some owners to keep and repair theirold vehicles rather than scrapping them. More-over, because vehicle prices are typically higherinside urban centers than outside, nonurbanowners of old vehicles would have an incentive tobring their vehicles to urban centers and sell themthere. These problems indicate that cash paymentby the government for old vehicles is not the bestuse of limited public resources.

Ensuring adequate credit

In lieu of offering cash payments, the morevaluable role for government is helping to ensurethe availability of credit through regular creditand micro-credit markets to urban public trans-port vehicle owners and drivers. This wouldfacilitate their replacing older autorickshaws—aswell as larger vehicles, such as diesel and two-stroke engine gasoline Tempos—with cleanerones.

Liberalizing trade in new vehicles

Liberalizing trade in new vehicles could also helpreduce emissions. Making the technology avail-able in the rest of Asia readily available toconsumers in South Asia would allow them tomeet tighter emission standards at lower cost.Rules such as local content requirements, basedon the infant industry argument, often result ininefficiency. High import tariffs, rigid licensingschemes, and quotas on foreign-made vehicles areall likely to slow the rate of vehicle renewal,preventing a decline in emissions.

Public Education

Emissions from two-stroke engines and repaircosts can be reduced by encouraging owners tocarry out regular maintenance and use lubricantspecifically manufactured for use in two-strokeengines at concentrations recommended by thevehicle manufacturer. Mass public education willbe needed to induce vehicle owners to adopt these“win-win” measures.

Governments, donors, and nongovernmentalorganizations have sought to raise public aware-ness about emissions in South Asia.� The Hydrocarbon Development Institute of

Pakistan has distributed pamphlets and

stickers containing basic information on thequality and quantity of gasoline and lubricant.

� In Dhaka, Bangladesh, the joint United NationsDevelopment Programme–World Bank EnergySector Management Assistance Programme(ESMAP) carried out a series of trainingsessions for mechanics and auto clinics forthree-wheeler taxi drivers in late 2000. Theprogram was based on the idea that the firststep toward adoption of good practice isdissemination of accurate information bymechanics to taxi drivers.

� A major public awareness campaign in Delhi,India, in late 1999 led to more than 66,000vehicles participating in free inspection andmaintenance clinics for two-wheelers (Iyer2000) (box 6).

Although public awareness initiatives havebeen taken throughout the region, many driverscontinue to maintain their vehicles inadequately.Much more needs to be done to improve publicunderstanding of the importance of propervehicle maintenance.

Future Directions

Two-stroke engines make up much of the totalvehicle fleet because they are relatively inexpen-sive, perform well in terms of power and speed,and are easy to repair. Precisely because two-stroke engines are so numerous and popular, anypolicy decision to address emissions from thesevehicles must take socioeconomic consequencesinto account. A large-scale immediate ban ongasoline-powered two-stroke engine vehicleswould be extremely difficult and costly, butfortunately numerous small and cost-effectiveimprovements are available. Public education andawareness raising—about the health impact ofemissions, the engine/fuel/lubricant parametersthat increase emission levels, simple steps driverscan take to reduce emissions, and the advantagesand disadvantages of various measures tabled formitigating air pollution—make emissions reduc-tion easier even with the existing vehicle fleet.

Two-stroke engine vehicles may eventually bephased out in South Asia, to be replaced bycomparable but cleaner alternatives that still meet


the social and economic needs of the public.Dynamic partnerships among government,industry, and the public will be crucial in thedevelopment of, and commitment to, achievingair quality goals. A transition period is likely,probably a number of years, during which in-usetwo-stroke engine vehicles in large urban centers

Box 6Reducing emissions and improving performance through free inspection and maintenance clinicsin Delhi

To reduce emissions, the Society of Indian Automobile Manufacturers (SIAM) and other Indian companies spon-sored voluntary inspection and maintenance clinics for two-wheelers in Delhi in 1999. The clinics, funded in partby the U.S. Agency for International Development, were held simultaneously in four locations in three phasesover four weeks. SIAM member companies provided 45 instruments and 200 staff. Major vehicle manufacturersstaffed and ran repair and information booths. Instrument manufacturers were on site to check instrument cali-bration and ensure the accuracy of emission measurements. The government of Delhi authorized SIAM to issue“Pollution under Control” stickers and stationed traffic police personnel at the clinic sites. The clinics were widelypublicized in the media, with appeals made by dignitaries, celebrities, and top-ranking government officials. Thecost of this highly successful program was about US$2.50 per driver.

Simple maintenance tasks were performed at the clinic, and booklets on maintenance and fuel-saving drivingtips were distributed. Vehicles were first checked for carbon monoxide and hydrocarbon emissions while idling.If the vehicle failed (that is, if carbon monoxide emissions exceeded 4.5 percent of the exhaust gas or hydrocarbonemissions exceeded 9,000 parts per million) it was taken to a repair booth where the carburetor was adjusted andemissions measured again. If the vehicle failed the second emissions test, the spark plugs were cleaned andadjusted and the air filter cleaned. A third emissions test was then run. After testing the vehicle was taken to thesafety booth, where the driver received a booklet of safety and maintenance tips.

About 80 percent of participating vehicles passed the idle carbon monoxide test; 95 percent of the remaining20 percent passed the test after minor repairs. Seventy-five vehicles that initially failed the emission tests weretested for fuel consumption. Fuel economy improved from an average of 39 to 47 kilometers per liter after minorrepairs, demonstrating the benefits of performing simple maintenance tasks. One of the four clinics had a smokemeter, and smoke measurements were taken of failing vehicles before and after the minor maintenance. Smokeemission levels fell after minor repairs.

are phased out. Under these circumstances, theimportance of promoting good practice in lubri-cant use in in-use two-stroke engine vehiclescannot be overemphasized. In this “win-win”situation vehicle emissions can be dramaticallyreduced and vehicle maintenance made easier atvirtually no cost.

31

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Nearly all vehicular particulate emissionsare extremely damaging to public health.Concentrations of total suspended

particles and particulate matter with an aerody-namic diameter of less than 10 microns (PM10)have been found to exceed internationally ac-cepted guidelines and standards severalfold inseveral South Asian cities. Even more damaging isfine particulate matter smaller than 2.5 microns(PM2.5). Other air pollutants from vehicularemissions that affect public health are lead (whereleaded gasoline is used), carbon monoxide, sulfuroxides, nitrogen oxides, ozone, and airbornetoxins.

Particulate Matter

PM10 and PM2.5 remain in suspension in the airfor hours or days and can travel significantdistances from the source. These particles enterthe respiratory tract, reaching deep into the lungs.PM10 includes all particles likely to pass throughthe nose and mouth. PM2.5 includes particles ableto reach the deeper parts of the respiratory tract,especially the alveolar regions of the lung. Animalstudies indicate that ultrafine particles (withdiameters of less than 0.05 microns) are clearedfrom the lungs only very slowly and can penetratethe pulmonary interstitium, where they causeinflammation.

The largest source of fine particulate formationis the incomplete combustion of fossil fuels andbiomass. Low fuel quality, inefficient combustion

processes, and poor vehicle and equipmentmaintenance all contribute to particulate emis-sions. Most particles generated from thecombustion and condensation of vapors arePM2.5. Most particles emitted from vehicles havediameters of less than a micron. Moreover, theseparticles are emitted near ground level, close towhere people live and work.

Primary particles are those emitted directlyfrom a source. Secondary particles are formedwithin the atmosphere, mostly from the chemicaloxidation of atmospheric gases. Vehicles contrib-ute to secondary particulate formation whenoxides of sulfur and nitrogen in the exhaust gasare transformed into sulfate-based and nitrate-based fine particulate matter in the atmosphere.

Isolating the effects of different types ofparticulate matter is difficult because otherpollutants—as well as other factors in the environ-ment, such as changes in temperature orepidemics of infections—also affect health. But aseries of extensive studies, mainly in the UnitedStates, has tied changes in particulate concentra-tions to changes in a wide range of healthindicators, including deaths, changes in lungfunction, emergency room visits, exacerbation ofasthma, hospital admissions, respiratory symp-toms, and time off from school or work (Holgateand others 1999).

These associations are stronger for particulateconcentrations than for other pollutants. Themeasurement of particulate-related death has

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been particularly well studied, and the results aremore consistent than those for other indicators.Although the composition of PM10 can varywidely from area to area and over time, the size ofthe estimated effects, particularly the effect ondeath rates, does not vary greatly with location.On the basis of these studies, the impact on publichealth may be considerably higher in South Asiathan in the United States because the quality ofmedical care is lower and people in urban areasspend more time outdoors.

PM10 has much more serious effects on healththan total suspended particles, which includeparticulate matter of all sizes. Coarse windblownparticles, for example—common in Delhi—are notbelieved to have a significant impact on health.Recent studies have indicated that the number ofparticles to which a person is exposed could bemore important than the aggregate mass.

Lead

In cities where leaded gasoline is still used,airborne lead poses a serious health threat. Theworst effects appear to be on the intellectual andbehavioral development of children. There hasbeen much public health interest in this issuebecause of mounting evidence that continualexposure to even low levels of lead, previouslyconsidered safe, could have a negative impact onchildren’s intelligence.

The absorption of lead from the environmentdepends on the chemical and physical characteris-tics of the lead as well as age, nutritional status,and physiological status. The amount of leadabsorbed by the body increases significantly whenthe stomach is empty. The rate of absorption isalso higher for children than for adults. Someevidence also suggests that more lead is absorbedby people with low dietary calcium intake or irondeficiency (World Health Organization 1995).These findings indicate that poor, malnourishedchildren are particularly susceptible to leadpoisoning.

Carbon Monoxide

Carbon monoxide is a colorless, odorless gas thatinhibits the capacity of blood to carry oxygen toorgans and tissues. High levels of carbon monox-

ide can cause people with chronic heart disease toexperience chest pain. Very high levels of carbonmonoxide can impair vision, manual dexterity,and learning ability and cause death.

Carbon monoxide is a product of the incom-plete combustion of fossil fuels. In most citiesgasoline-fueled vehicles account for most carbonmonoxide emissions. The level of carbon monox-ide emissions can be reduced by incorporatingoxygenates in gasoline for old vehicles and byusing oxidation catalysts in new vehicles.

Sulfur Oxides

Sulfur dioxide, one of the oxides of sulfur, causeschanges in lung function in asthmatics andexacerbates respiratory systems in sensitiveindividuals. Sulfur oxides are formed when fossilfuels containing sulfur are burned. These oxidescontribute to acid rain and to the formation ofsecondary particles. The amount of sulfur emittedis directly proportional to the amount of sulfur inthe fuel. It can be reduced by treating the fuel, forexample, through hydrotreating, or by installingsulfur removal devices at the point of emission,such as flue gas desulfurization units at powerplants.

Nitrogen Oxides

Nitrogen dioxide, one of the oxides of nitrogen,causes changes in lung function in asthmatics.Nitrogen oxides are formed during combustion asnitrogen in the air reacts with oxygen at hightemperature. Like sulfur oxides, these oxidescontribute to both acid rain and secondaryparticulate formation. Nitrogen oxides are alsoprecursors of ground-level ozone.

Power plants and diesel- and gasoline-fueledvehicles emit nitrogen oxides. The amount ofnitrogen oxide formed can be reduced by control-ling the peak combustion temperature—forexample, by recirculating exhaust gas in vehicles;reducing the amount of oxygen available duringcombustion; or converting nitrogen oxides tooxygen-containing inorganic compounds andnitrogen—for example, by installing three-waycatalytic converters.

33Annex A — Health Impact of Air Pollution

Ozone

Ozone causes photochemical smog and has beenassociated with transient effects on the humanrespiratory system, particularly the decline inpulmonary function during light to heavy exer-cise. Gasoline-fueled vehicles are a significantsource of volatile organic compounds, whichalong with nitrogen oxides are precursors ofozone. Ozone abatement is complicated bynonlinear interactions among ozone precursors—the amount of ozone formed is not directlyproportional to the ambient concentrations ofvolatile organic compounds and nitrogen oxides

but is a complex function of a number of factorsthat include the ratio of these two precursors. It istherefore important to collect relevant data andunderstand the chemistry of ozone formationbefore selecting mitigation measures.

Toxic Airborne Emissions

Toxic emissions from vehicles include benzene;polycyclic aromatics; 1,3-butadiene; and alde-hydes. All of these are carcinogens, according tothe World Health Organization, which providesguidelines for ambient concentrations.

35

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AEA Technology in the United Kingdomconducted an experimental program tofind a more reliable particulate sampling

technique (Smith 2000). The experiment investi-gated two aspects of particulate sampling:� Whether passing gas through a filter coated

with liquid deposit causes any loss of thatliquid.

� Whether significant amounts of oil are lost inthe sampling pipes into and including theconstant volume sampling (CVS) system.

To try to answer the first question, AEAcompared the use of an Andersen impactor—inwhich particles are deposited on filter paperswithout gas passing through the paper—with thestandard regulatory filter method. The secondquestion was investigated by taking particulatesample from raw exhaust very close to a motor-cycle under steady state conditions andcomparing the results with CVS measurements.

A 1974 twin-port, two-stroke, single-cylinderJawa 250 cubic centimeter motorcycle manufac-tured in Czechoslovakia was used for theexperiments. The vehicle had 39,500 kilometers onthe odometer and no emission control. It operatedwith unleaded gasoline at a ratio of 30 to 1 withCastrol Super TT two-stroke oil that met JASO FBand API TC specifications. The lubricant andgasoline were premixed.

A Horiba microdilution system (MDLT-1300)was installed very near the motorcycle’s exhaust

to capture sample from the hot exhaust gas beforeit had a chance to cool to ambient temperature.The flow to the microtunnel was constant; theremaining flow to the CVS depended on engineconditions.

The exhaust gases were mixed with filtereddilution air in the dilution tunnel (internal diam-eter 21.5 centimeters), with the CVS pumpproviding a constant volume flow through thedilution tunnel. A standard regulatory filtersample for particulate matter was taken from thedilution tunnel onto 47 millimeter diameterPallflex type TX40HI20-WW filters.

In addition to this method, an Andersenimpactor was used to measure particulate emis-sions. The Andersen II Cascade Impactor isdesigned to measure the mass-weighted sizedistribution of aerosol particles up to an aerody-namic diameter of about 10 microns. Theinstrument is a multistage, multijet device thatseparates particles into size classes based on theirinertia. An impactor stage consists of a series ofjets over a flat collection medium (filter) at apreset distance. Aerosol passing through each jetis directed against the filter, causing the fluidstreamlines to be deflected through 90°. Particleswith high inertia are unable to follow the stream-lines and impact on the collection medium;particles with a sufficiently low inertia follow thestreamlines and miss the collection plate.

The investigators used two impactor stages.The first collected particles with diameters of

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0.3–10 microns. The second collected particleswith diameters of less than 0.3 microns. Thismethod differs significantly from the standardregulatory method because the gas flows aroundthe paper instead of through it, eliminating thepossibility of liquid droplets being bubbledthrough the paper because of the gas flow.

Because the total exhaust volume flow ratefluctuates, steady state experiments were con-ducted to be able to use the data obtained usingthe Horiba filters. The motorcycle was drivenuntil reasonably stable conditions were obtained,and an average over 10 minutes was taken.

The motorcycle itself caused the greatestproblem for obtaining reproducible results.Because the engine was unstable, it was notfeasible to use the equivalent of a dead man’s footon the motorcycle. The steady states thus had tobe manually driven.

Data were also taken at idle, at 30 and 50kilometers per hour steady states, and at anEconomic Commission for Europe (ECE) transientdriving cycle. The ECE cycle could not be fol-lowed exactly because the motorcycle was unableto drive the cycle with the required gear changes.The cycle was run as an example exercise only.

Data were collected over three days (table A1).Deposits on the filter papers were gray-brown incolor, typical of oil deposits. Solvent extraction ona selection of filter papers removed 98–99 percentof deposits.

The data from the regulatory and Horibamicrotunnel systems were similar, particularlywhen the uncertainty in the microtunnel measure-ments was taken into account. The results suggestthat condensation along the sampling lines andCVS is not a major problem and that the Andersenimpactor yields masses about 60 percent higherthan the other two techniques.

The CVS flow did not have a significantimpact on the results within the experimentalreproducibility of the driving conditions. At theend of the experiments the CVS system was takenapart. There was no evidence of significantfouling by oily deposits in the dilution tunnel,although there was a little oily soot in the heatexchanger. Fuel consumption from the transientcycle was calculated to be about 23 kilometers perliter using a carbon mass balance.

The relation between the particulate emissionsmeasured by the Horiba microtunnel and regula-

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Run

Constant volume

sampling flow

(cubic meters

per minute)

Road speed

(kilometers

per hour)

Regulatory

particulate

(grams per

kilometer)

Andersen

impactor

particulate

(grams per

kilometer)

Horiba

microtunnel

particulate

(grams per

kilometer)

Smoke

opacity

(percent)

Percent of

particles larger

than 0.3

microns

1 9.0 30 0.098 — 0.080 15 —

2 4.4 30 0.116 0.167 — 20 90

3 2.9 30 0.112 0.184 0.100 23 90

4 9.0 30 0.123 0.186 0.126 — 95

5 9.0 30 0.141 0.223 0.129 25 89

6 4.4 30 0.128 0.200 0.117 19 87

7 2.9 30 0.125 0.224 0.108 21 84

8 9.0 30 0.081 0.129 0.075 13 82

9 4.4 30 0.101 0.149 0.092 17 83

11 9.0 0 0.014a 0.026a 0.021a 28 84

12 9.0 50 0.056 0.093 0.054 14 78

13 9.0 ECE cycle 0.611 0.984 — — 91

37Annex B — Improving Particulate Sampling of Two-Stroke Engine Vehicles

tory techniques suggests that little sample is lostto condensation. Uncertainties in exhaust flowdetermination mean the two measurements arenot identical, but the ratio between the twomeasurements is constant. The absence of sampleloss is confirmed by the lack of fouling of the CVSdilution tunnel by oil droplets. However, therewas evidence that the heat exchanger, with itsmuch smaller diameter tubes, does cause dropletcondensation. In the dilution tunnel, whosediameter is 21.5 centimeters, the interaction withthe walls is minimized; in the heat exchanger,however, the interaction with the walls causesdroplet condensation. This does not affect particu-late measurements, which are made before theheat exchanger.

The higher results from the Andersen impactorseem to suggest loss of sample from the regula-

tory filter. However, under the conditions underwhich the system was operated, the relationbetween the Andersen and regulatory data islinear. Therefore, even if some systematic lossesdid occur, the use of the regulatory method wouldprovide a satisfactory comparative method: theabsolute values may not be exactly correct, but thecorrelation between vehicles and oils would bevalid.

The Andersen data imply that about 90 percentof the particulates (by mass) have diameters ofmore than 0.3 microns. These are likely to be oildroplets, as suggested by the color of the depositsand the solvent extraction results, which implythat 98–99 percent of the deposits are from oil.

39

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Regulatory decisions for the managementof urban air quality should be based onobjective assessment of scientific and

technical evidence and thorough cost-benefitanalysis of alternative air quality improvementstrategies. Timely information about air quality,emissions, and health and other benefits ofreducing emissions is needed to conduct cost-benefit analysis.

Air quality monitoring and reporting need tobe upgraded to internationally acceptable stan-dards and made available to the public daily.Reliable and complete inventories of emissionsfrom different sources (domestic, industrial,different transportation modes, resuspended dust)are crucial for identifying priority areas forinterventions. Air quality modeling then needs tobe conducted based on the monitoring andinventory data to identify the main sources ofambient pollution in the areas where the largestnumber of people are at risk. The health and otherbenefits of reducing emissions then need to becomputed and compared for different mitigationmeasures.

The reliability of the emissions inventorydepends on the accuracy of the data on emissionfactors and consumption of fuels used in differentsectors. But reliable data on emissions by thetransport sector are scarce in developing coun-

tries. Vehicular emission factors are a function offuel quality—for example, the level of sulfur ingasoline and diesel fuel—and vehicle technol-ogy—for example, the level of maintenance andthe nature of exhaust treatment devices. The U.S.Environmental Protection Agency’s highwayvehicular emission factor model contains a fairlycomprehensive list of vehicular emission factors,but the data do not reflect the condition of ve-hicles in developing countries.

Several software programs are available tobuild emissions inventories for both mobile andstationary sources. The Decision Support Systemfor Integrated Pollution Control is based on theWorld Health Organization’s emission factors.The International Petroleum Industry Environ-mental Conservation Association’s Urban AirQuality Management Toolkit is one of only a fewmodels that takes into account the effects of fuelcomposition on emission factors. It is linked to amodel that calculates incremental costs fordifferent mitigation options.

The World Bank has recently built an Excelspreadsheet–based transport emissions inventoryprogram, VAPIS (Vehicular Air Pollution Informa-tion System). The program computes past andfuture vehicular emissions as a function of vehicletype, year, and fuel used for several pollutants. Itprojects future vehicle growth and emissions.

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41

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Energy and Environmental Analysts, Inc. 1998.“Technology and Policy Options to ControlThree-Wheeler Emissions in Dhaka.” January.

Loksha, Victor. 1997. “An Analysis of the ElectricVehicle Option Based on the Experience of theElectric Tempo Three-Wheelers Piloted inNepal and a Similar Project Proposed inBangladesh.” October 27.

_____. 1997. “Finding Alternatives to PollutingTwo-Stroke Engine Vehicles in South Asia.”April 29.

Matskovski, Anton. 1997. “Reducing Emissionsfrom Two- and Three-Wheelers in India:

Market Description and Policy Analysis.”November 3.

South Asia Environment Sector ManagementUnit. 1998. “The Cost of EnvironmentalRemediation in India: The Example of AirPollution by Two-Stroke Engine Vehicles.”February 23.

Xie, Jian, Jitendra J. Shah, and Carter J. Brandon.1998. “Fighting Urban Transport Air Pollutionfor Local and Global Good: The Case of Two-Stroke Engine Three-Wheelers in Delhi.” April.

!�%��% �� '��

43

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1. Another pollutant of concern is lead, althoughlead in gasoline has been phased out inBangladesh and India. Pakistan and Sri Lankaare two countries where leaded gasoline isstill widely used.

2. If leaded fuel is used, two-stroke engines emitorganic lead, which is much more damagingto public health than the inorganic leadformed by the full combustion of leadadditives.

3. Tests done at ARAI (the Automotive ResearchAssociation of India) in the fall of 2000indicate emissions reductions of thismagnitude, but require further analysis.

4. As the size of the program—and subsidy—grew, the government could not afford tocontinue bearing the cost. When the subsidieswere reduced the use of CNG felldramatically. Without subsidies CNG useproved to be unsustainable.

5. This is also because the standards forhydrocarbon emissions in 2003 are twice asstringent for two-stroke than for four-stroketwo-wheelers.

6. Two-stroke engine vehicles produce morenoise than four-stroke gasoline enginevehicles, but four-stroke diesel engines arenoisier than either type of gasoline engine.

7. Lead is added to gasoline as an organiccompound to improve its combustioncharacteristics.

8. In India most electricity is generated byburning coal, which emits about twice asmuch carbon dioxide as natural gas per unitof electricity generated. Thus where coal isburned, switching to electric vehicles will notnecessarily reduce greenhouse gas emissions.

9. The research octane number is a measure of agasoline’s resistance to self-ignition(knocking) when vehicles are operated at lowspeed corresponding to city drivingconditions.

10. The motor octane number is a measure of agasoline’s resistance to self-ignition(knocking) when vehicles are operated underhighway driving conditions.

11. There is no consensus on the best type ofbattery for the future.

45

!�� (�� %��

Auto/Oil Air Quality Improvement ResearchProgram. 1997. Program Final Report.

ARAI (Automotive Research Association ofIndia.). 1998. “Monitoring of In-Use VehicleEmissions.” Paper presented at the Workshopon Integrated Approach to Vehicular PollutionControl, April 16-18, Delhi, India.

Caines, A. J., and R. F. Haycock. 1996. AutomotiveLubricants Reference Book. Warrendale, Penn.:Society of Automotive Engineers, Inc.

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Cumming, R. B. 1997. “The InternationalPerspective.” International Association forNatural Gas Vehicles Newsletter 45.

Danielson, Eugene. 1978. “ParticulateMeasurement Motorcycle Test Results.” NTISPublication PB80-115983. Ann Arbor, Mich.:U.S. Environmental Protection Agency.

Faiz, A., C. S. Weaver, and M. P. Walsh. 1996. AirPollution from Motor Vehicles: Standards andTechnologies for Controlling Emissions.Washington, D.C.: World Bank.

Holgate, S. T., J. M. Samet, H. S. Kore, and R. L.Maynard, eds. 1999. Air Pollution and Health.London: Academic Press.

Huang, H. H., M. H. Jeng, N. T. Chang, Y. Y. Peng,J. H. Wang, and W. L. Chang. 1993.“Improvement of Exhaust Emissions on Two-Stroke Engine by Direct-Injection System.” SAEPaper 930497.

International Energy Agency. 1997. “CO2

Emissions From Fuel Combustion.” DisketteService Documentation, International EnergyAgency, Organisation for Economic Co-operation and Development, Paris, France.

Iyer, N. V. 1999. “Technology for Cleaner Two-and Three-Wheelers: Achievements and FutureChallenges.” Paper presented at theConfederation of Indian Industry TechnologySummit and Platform, October 28–29,Hyderabad, India.

———. 2000. “Emissions and Control Options forTwo-Stroke Engines in India.” Paper presentedat the Workshop on Pollution fromMotorcycles: Issues and Options, March 9,World Bank, Washington, D.C.

Kirchberger, R. S. 2000. “Future Prospects of Two-Stroke Engines and Possible TechnicalSolutions for East/South Asian Markets.”Paper presented at the Workshop on Pollutionfrom Motorcycles: Issues and Options, March9, World Bank, Washington D.C.

MECA (Manufacturers of Emission ControlsAssociation). 1999. “Emission Control of Two-and Three-Wheel Vehicles.” Washington, D.C.


Moulton, Peter, and Marilyn Cohen. 1997.“Introducing Electric Vehicles in theDeveloping World.” Paper presented at EVS-14International Electric Vehicle Symposium,December, Orlando, Florida.

Palke, D. R., and M. A. Tyo. 1999. “The Impact ofCatalytic Aftertreatment on Particulate MatterEmissions from Small Motorcycles.” SAEPaper 1999-01-3299.

Radian International. 1998. “Particulate MatterAbatement Strategy for the BangkokMetropolitan Area: Final Report.”

Smith, Allan P. 2000. “Assessment of ParticulateSampling for Two-Stroke Vehicles.” AEATechnology Report submitted to the WorldBank, Washington, D.C.

Southwest Research Institute. 1973. “ExhaustEmissions from Uncontrolled Vehicles andRelated Equipment using Internal CombustionEngines: Part 3, Motorcycles.” San Antonio,Tex.

World Health Organization. 1995. EnvironmentalHealth Criteria 165: Inorganic Lead. World HealthOrganization, Geneva.

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