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Treatment of Junctions- Volume I: Final Report

Treatment of Junctions

FINAL REPORT

Volume I

Section B6: Boralesgamuwa

Transportation Research and Study Centre

University of Moratuwa

Sri Lanka

15th

January 2010


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Table of Contents

CHAPTER 1 - INTRODUCTION ___________________________________________________________ 1-1

1.1 Study Area ________________________________________________________________________ 1-2

1.2 Scope ____________________________________________________________________________ 1-6

1.3 Data Collection ____________________________________________________________________ 1-6

CHAPTER 2 - TRAFFIC ANALYSIS _______________________________________________________ 2-1

2.1 Turning Movement Counts ___________________________________________________________ 2-1

2.2 Link Movements ___________________________________________________________________ 2-3

2.2.1 Colombo-Horana Road ____________________________________________________________ 2-3

2.2.2 Dehiwala-Maharagama Road _______________________________________________________ 2-4

2.3 Pedestrian Movements______________________________________________________________ 2-4

2.4 Speed and delay ___________________________________________________________________ 2-6

2.5 Accident Studies ___________________________________________________________________ 2-7

2.6 Road Infrastructure _________________________________________________________________ 2-8

2.6.1 Highway Geometry of the Study Area _______________________________________________ 2-11

2.7 Summary of Problems _____________________________________________________________ 2-12

CHAPTER 3 - PROPOSED SOLUTIONS __________________________________________________ 3-1

3.1 Junction Control ___________________________________________________________________ 3-1

3.1.1 Flyover Option ___________________________________________________________________ 3-1

3.1.2 Signalization _____________________________________________________________________ 3-5

3.2 Traffic Management Measures _______________________________________________________ 3-8

3.2.1 Parking Control __________________________________________________________________ 3-9

3.2.2 Access Control ___________________________________________________________________ 3-9

3.2.3 Segregated pedestrian facilities _____________________________________________________ 3-9

3.2.4 Geometric improvements to the intersection _________________________________________ 3-10

3.2.5 Location and Design of bus stops and bus bays ________________________________________ 3-10

3.2.6 Re-routing of buses ______________________________________________________________ 3-10


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CHAPTER 4 - ECONOMIC ANALYSIS _____________________________________________________ 4-1

4.1 Costs _____________________________________________________________________________ 4-1

4.2 Benefits __________________________________________________________________________ 4-2

4.2.1 Traffic Analysis ___________________________________________________________________ 4-2

4.2.2 Economic Benefits ________________________________________________________________ 4-4

4.3 Cost-Benefit Analysis _______________________________________________________________ 4-8

4.3.1 Signalization Option ______________________________________________________________ 4-8

4.3.2 Flyover Option ___________________________________________________________________ 4-9

4.4 Non-Quantifiable Benefits __________________________________________________________ 4-10

CHAPTER 5 - CONCLUSIONS _____________________________________________________________ 5-1

CHAPTER 6 - RECOMMENDATION ______________________________________________________ 6-1


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List of Tables

Table 1-1: Details of Surveys Carried Out _____________________________________________ 1-6

Table 2-1: ADT (two days average) on Links __________________________________________ 2-1

Table 2-2: Peak Pedestrian Movements on Main Links ___________________________________ 2-5

Table 2-3: Two days hourly average speed of each turning of the roundabout _________________ 2-7

Table 2-4: Summary of Road Accidents in Study Area (Year 2007) _________________________ 2-7

Table 2-5: The cross sectional details of the road links in the study area. _____________________ 2-9

Table 2-6: Details of Three Wheeler Parking in the Study Area ___________________________ 2-10

Table 2-7: Details of the Important Land Use in the Study Area ___________________________ 2-11

Table 2-8: Existing Geometric Properties of the Approach Links of the Intersection ___________ 2-11

Table 3-1: Split of total vehicle turns at Boralesgamuwa Roundabout________________________ 3-1

Table 4-1: Comparative Cost Estimate of Options in 2008 prices ___________________________ 4-2

Table 4-2 : Comparison of Speed ‘Before and After’ ____________________________________ 4-3

Table 4-3: Economic Analysis for Signalization Option __________________________________ 4-5


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Table of Figures

Figure 1-1 : Study Area ____________________________________________________________ 1-2

Figure 1-2: Site map for the approximate length of the study area ___________________________ 1-3

Figure 1-3: Typical Road Conditions in the Study Area ___________________________________ 1-5

Figure 2-1 : Traffic Flow Diagrams (ADT by major vehicle groups)*Projected Traffic Data from

Traffic Survey of 2007 October _____________________________________________________ 2-2

Figure 2-2 : Special problems observed at site. _________________________________________ 2-3

Figure 2-3 : Hourly link flow of the intersection ________________________________________ 2-4

Figure 2-4 : Total daily pedestrian movement at Boralesgamuwa roundabout _________________ 2-5

Figure 2-5: Hourly Pedestrian flows across each road links at the intersection _________________ 2-6

Figure 2-6: Road Link Configuration of Boralesgamuwa Roundabout _______________________ 2-8

Figure 2-7: Three Wheeler Parking Locations in the Study Area ____________________________ 2-9

Figure 2-8: Locations of Important Land Use in the Study Area ___________________________ 2-10

Figure 2-9 : Proposed Lane Arrangement of the Intersection. _____________________________ 2-12

Figure 2-10: Longitudinal Section along B84 Road at the Roundabout ______________________ 2-12

Figure 3-1: Vertical Alignment of the flyover along Colombo-Horana Road (B084) ____________ 3-2

Figure 3-2: Horizontal Alignment of Flyover along B84 Road with existing Road Layout (Cantilever

Bridge). ________________________________________________________________________ 3-3

Figure 3-3: Horizontal Alignment of the Flyover along the Colombo Horana Road with a Straight

Segment. _______________________________________________________________________ 3-4

Figure 3-4: Road sections to be improved under signalization of the intersection. ______________ 3-6

Figure 3-5: Lane Arrangement of the Intersection for Signalization _________________________ 3-7

Figure 3-6: Signal Timing for Boralesgamuwa _________________________________________ 3-8

Figure 6-1: Map of Boralesgamuwa Study Area showing recommended improvements _________ 6-2


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CHAPTER 1 - INTRODUCTION

Boralesgamuwa Intersection is made by the crossing of the Colombo-Horana Road (B084) by the

Dehiwala- Maharagama Road (B094) at around the 12.5km distance from Colombo Fort. This

junction is an important suburban node for road transportation since:

• The north –south oriented Colombo-Horana Road (B084) is one of the primary

commuter traffic corridors to the city located between the Galle Road (A002) and High-

Level Road (A004) both of which are trunk roads connecting major provincial towns.

• The Dehiwala-Maharagama Road (B94) that crosses this junction at Boralesgamuwa is

one of the heavily used orbital road links in the East-West direction. This is located 6km

north of the Piliyandala Junction which is the next orbital road link and 3 kms north of

Kohuwela which has a similar connection.

• Its geographic location is just on the periphery of the Colombo Municipal and in a fast

developing suburban area.

• In addition to Colombo city it provides direct connections to three suburban centres in

the southern part of Colombo District. These being Piliyandala, Dehiwala and

Maharagama.

The intersection presently has a roundabout arrangement. This is a small roundabout with radius of

4.8 metres and has two lanes for each of its approaches for up to a short distance from the junction.

Beyond that all roads become two lane roads. The Colombo-Horana Road which carries the larger

traffic is a major commuter artery, with comparison to the Dehiwala-Maharagama Road. (B094)

However this major road has not been improved by any means for a long time but the Dehiwala-

Maharagama Road (B094) which is the orbital connector road has recently been completed with

asphalt surfacing. On the other hand the condition of the Colombo-Horana Road is very poor with

many potholes and uneven surfaces along the entire stretch of road from Horana to Havelock Town.

This situation is most sever in the immediate vicinity of the Boralesgamuwa junction particularly on

the section of road towards Piliyandala

The junction is also at the crest of a curve on the Colombo-Horana Road (B084). Each of the

approaches has around 200 metres of road frontage developed for commercial activities mostly in

terms of retail trade and services. In the case of the southern approach from Horana direction, this

length extends to about 300 metres. There is a moderate amount of activity associated with these

developments which attracts vehicular traffic as well as pedestrians. This causes an increase in the

intensity of road use around the junction with heavy demand for parking as well as for pedestrian

crossings which includes passengers transferring between buses.

The junction regularly gets congested during peak hours. The conflicts arising from the intersection of

the traffic flows and the activities arising from commercial developments are noticeable throughout


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the day culminating in large delays in the evening especially for traffic returning from Colombo. This

congestion increases during rainy weather conditions.

1.1 Study Area

The Scope of the study covered in this report is confined to examining the possible short term and

long term cost effective solutions to the traffic congestion which can be carried out by junction

improvement only. Hence the specified study area to be investigated would be confined to a very

small area extending around 500 to 600 meters from the centre of the junction.

There are no other junctions and

road links within this area. There

is one local road of some interest

to traffic management called

Aberatna Mw connected to the

Colombo- Horana Road (B084) at

a distance of around 200 metres

towards Piliyandala which

provides a connection by passing

the junction to the Dehiwala-

Maharagama Road (B094) on to

the Dehiwala link. This is a two

lane road but mainly serves as an

access road to residential areas.

This road link is not attractive

enough due to the capacity and the

poor highway geometry to serve as

a through road or as a by-pass road

to divert traffic movements

between the Piliyandala link and

the Dehiwala Link even if it is

improved in the future.

Figure 1-1 : Study Area

The buildings by the road side on all four road links within the study area do not exceed three floors

and typically signify the scale of development of a junction as opposed to a town centre. The most

important services available are confined to a supermarket, few banks, a police station, several retail

shops, hardware stores and small scale offices.



The junction serves as an important

served by a bus route between Dehiwala and Maharagama in the east

routes in the north-south direction

Boralesgamuwa junction itself. Therefore no bus terminals or parkin

the study area at the moment.

However there are several three wheeler parks

junction. Apart from three wheeler parking, t

parking throughout the day. Parking

at any time of the day. A significant

small and medium trucks, delivery vans and h

parking. But parking can be seen

obstructing the pedestrian traffic flows.

There are no satisfactory pedestrian facilities alongside the roads

few metres of raised walkways with cu

parked vehicles.

The trace of the road and the commercial development

either side of the Boralesgamuwa roundabout

in the study area described earlier is given in

Figure 1-2: Site m

Volume I: Final Report

n important transit centre for bus passengers. The Boralesgamuwa junc

Dehiwala and Maharagama in the east-west direction and several

south direction. However there are no buses that originate from

junction itself. Therefore no bus terminals or parking for buses are required within

three wheeler parks at the junction itself and along the approaches

Apart from three wheeler parking, the study area has a significant demand for on

Parking on both sides of the road on all four approach roads

A significant fraction of these parked vehicles are commercial vehicles such as

small and medium trucks, delivery vans and hand tractors. There are no marked stalls for on

parking. But parking can be seen on the paved shoulders and on raised walkways everywhere

flows. There is no parking control implemented in the study area.

There are no satisfactory pedestrian facilities alongside the roads within the study area

metres of raised walkways with curbs, but they are un-paved. These also are usually occupied

mercial development along the Colombo- Horana Road (

Boralesgamuwa roundabout is shown in Figure 1.1. The condition of road and traffic

is given in Figure 1.2.

map for the approximate length of the study area

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The Boralesgamuwa junction is

west direction and several

originate from the

required within

approaches to the

he study area has a significant demand for on street

approach roads can be seen

commercial vehicles such as

stalls for on-street

paved shoulders and on raised walkways everywhere

implemented in the study area.

within the study area. There are a

also are usually occupied by

Horana Road (B084) on

ondition of road and traffic


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Boralesgamuwa Roundabout

New Surfacing on Dehiwala –Maharagama Rd

Right-of-Way width on Horana-Colombo Rd (towards

Piliyandala)

Lack of Walkway Facilities

Inadequate and Unattractive Walkways (Horana Rd)

Pedestrian Crossing Near Police Station (Horana Rd)



Figure 1-3: Typical Road Conditions in

Traffic flow on B84 Horana-Colombo Rd

Piliyandala)

Parking, Lottery Outlet, and Pedestrians at Junction

Three Wheeler Park right at the Corner of the Junction


: Typical Road Conditions in the Study Area

Colombo Rd (Towards

Right-of- Way of Abey

Parking, Lottery Outlet, and Pedestrians at Junction Maneuvering Parked Vehicles Across the Road near

the Junction

Three Wheeler Park right at the Corner of the Junction

Bus Halt without Bus Bays at the Junction (Horana

Road)

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yrathna Mw Entrance

Parked Vehicles Across the Road near

the Junction

Bus Halt without Bus Bays at the Junction (Horana

Road)


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1.2 Scope

The scope of work reported herein as agreed upon with the Road Development Authority, include the

following:

• Analysis of Turning Movement Counts, Pedestrian Counts, Traffic Delay Counts or a full

traffic survey of the local area as the case may be, in order to obtain a clear picture of the

cause of the traffic congestion and to identify the remedies.

• Comprehensive analysis of traffic patterns including movement of pedestrians, parking,bus

circulating, in and out movements of bus stands and bus halting.

• Analysis of traffic accidents at such junctions.

• Consider the influence of other problems such as heavy inflows, out flows of traffic from and

to adjacent by-roads, misuse of road space etc.

• Identify the problems in the existing set up such as erroneous road markings, signs, signal

lights with faulty phases, lack of capacity for turning circles, inadequate lane widths etc.

• Calculation of benefits for technically feasible alternatives.

• Calculation of economic benefits for the above alternatives

• Based on above, recommend suitable solutions for each location which will include, solutions

such as new or improvements to signals, roundabouts, flyovers, over passes, traffic

management schemes, etc.

• If over passes/ flyovers required conceptual design of them with appropriate dimensions,

required legs etc.

• Report on the impact on Urban architecture

1.3 Data Collection

The Table 1-1 shows the details of the survey locations and type of surveys carried out pertaining to

this study. Surveys were carried out using a pool of 20 university students who were specifically

trained and worked in groups under an experienced survey supervisor. The details of how the surveys

were carried out are given in the Appendix.

Table 1-1: Details of Surveys Carried Out

Survey Date Locations

Travel Time Survey 5th & 11th October 2007 200 m from the junction

Turning Movement Counts (Classified) 16 Oct 2007 TM8 : Boralesgamuwa Junction

Pedestrian Counts 15 Oct 2007 200 m from the junction

Turning Movement Counts (Total) 21 Aug 2008 TM8 : Boralesgamuwa Junction


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CHAPTER 2 - TRAFFIC ANALYSIS

2.1 Turning Movement Counts

The results of the turning movement counts which show the movements by each vehicle type at the

Boralesgamuwa intersection is given in the Appendix. The tables and graphs given there are shown in

the following forms:

• Hourly total of all vehicle types for each approach and ADT for each approach

• Graph showing the variation of flow by each vehicle type for each approach

• Graph showing the variation of flows by each approach for all vehicle types

The summary of the traffic flows estimated from two days average of 2007 data in each approach of

the intersection are given in the following Table. It can be seen that there are over 53,000 vehicle

movements per day at the Boralesgamuwa intersection. Of this the passenger vehicle flows make up

over 85% of the intersection traffic flow.

Table 2-1: ADT (two days average) on Links1

Junction

Road ADT

Passenger

Vehicles

Buses Goods

Vehicles

Non

Motorized

Total

(including other

vehicle types)

B084 :

Horana Road

(A) 27,045 1,765 2,916 77 32,201

B094 :

Maharagama

Road (B) 15,201 769 1,644 56 17,957

B084 :

Horana Road

(C) 28,613 1,812 3,375 99 34,367

B094 :

Maharagama

Road (D) 19,321 816 2,179 58 22,794

The following Figures show the ADT for each vehicle type in the study area as well as the total ADT

by link of the road network

As per the traffic survey conducted in this year, the ADT on Colombo-Horana Road (B084) is above

36,000 vehicles per day. The maximum flow of 36,614 vehicles per day occurs on the Piliyandala

Link. On the Colombo Link the maximum is 32,620 vehicles per day. Maximum flow on the

Maharagama link (B094) is 21,031 per day. The lowest ADT is on the Dehiwala Link.

1 Estimated from 2007 Traffic Data


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Maximum peak traffic flow has been recorded in the evening is 5,350 vehicles per hour at the

junction. Maximum peak flow on the Piliyandala Link is 4,105 vehicles per hour which is the highest

hourly link flow at the junction. This seems to be a congested flow condition when comparing the

road capacity of an undivided two lane road which should be taken as around 2,800 vehicles per hour.

A: *ADT of Passenger Vehicle Flows at the

Roundabout

B: *ADT of Non-Motorized Vehicle Flows at the

Roundabout

C: *ADT of Bus Flows at the Roundabout

D: *ADT of Goods Vehicle Flows at the

Roundabout

E: *ADT of Total Flows at the Roundabout

(2007)

F: ADT of Total Flows at the Roundabout

(2008)

Figure 2-1 : Traffic Flow Diagrams (ADT by major vehicle groups)*Projected Traffic Data from

Traffic Survey of 2007 October



There are 2.580 buses travelling across

the roundabout. This is a very insignificant number comp

There are 5,057 goods vehicle movements

traffic flow.

2.2 Link Movements

2.2.1 Colombo-Horana Road

The Colombo-Horana Road (B084) handles between 3,000 to 4,

during the am peak, while during the pm peak this increases to between 3,500 to 4,500 vehicles per

hour. Most of the congestion on the

over a length of around 500m to 700m. This area has a high density of commercial activities, and

hence many ad hoc parking activities takes place

hand tractors, uneven roof and plinth projections of temporary shops and workshops,

unpaved and uneven shoulders, corrugated road surface etc also contributes to reduc

capacity in this section. Some of the issues leading to

Horana Road are illustrated in Figure

Row of Hand Tractors Park on the

periods of time

Lottery Selling Point on the sidewalk and

pedestrians using carriageway

Figure 2


across this roundabout per day. Only 141 bicycle trips are found at

the roundabout. This is a very insignificant number compared to other town areas such as at

movements recorded at the junction. This is around 9% of the total

Horana Road

84) handles between 3,000 to 4,000 (Figure 2.2) vehicles per hour


hour. Most of the congestion on the Dehiwala-Maharagama Road takes place on the Piliyandala link

0m to 700m. This area has a high density of commercial activities, and

hoc parking activities takes place alongside the road. The slow moving vehicles like

hand tractors, uneven roof and plinth projections of temporary shops and workshops,

unpaved and uneven shoulders, corrugated road surface etc also contributes to reduc

Some of the issues leading to the reduction in road capacity on Colombo

Horana Road are illustrated in Figure 2.2.

the treet for long Parking at Opposite Direction, Open Drains

reducing available capacity

Lottery Selling Point on the sidewalk and

pedestrians using carriageway Lack of Pedestrian Facilities resulting

pedestrian activity on the carriageway

2-2 : Special problems observed at site.

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Only 141 bicycle trips are found at

other town areas such as at Panadura.

This is around 9% of the total

.2) vehicles per hour


takes place on the Piliyandala link

0m to 700m. This area has a high density of commercial activities, and

The slow moving vehicles like

hand tractors, uneven roof and plinth projections of temporary shops and workshops, open drains,

unpaved and uneven shoulders, corrugated road surface etc also contributes to reducing the road

road capacity on Colombo –

Parking at Opposite Direction, Open Drains

reducing available capacity

Lack of Pedestrian Facilities resulting in much

pedestrian activity on the carriageway


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2.2.2 Dehiwala-Maharagama Road

It is observed that the commercial land use density along the Dehiwala-Maharagama Road (B094) is

much higher than the Colombo-Horana Road. A number of new high rise commercial buildings have

been built after the recent improvement of the road. Generally no raised and kerbed walkways are

provided on this road except for a short distance in front of the market side on the Maharagama Link.

This too is occupied by three wheelers and other vehicle parking. The Dehiwala-Maharagama Road

carries a maximum of 2,000 vehicles per hour at peak hours (Figure 2.3). This vehicular flow can be

easily handled with the four lane road configuration available on the Dehiwala-Maharagama Road

close to the junction. However, often the moving traffic is obstructed by parked vehicles, vehicle

maneuvering in and out of commercial establishments, pedestrians on the carriageway, etc. Therefore,

the solutions are needed to minimize such events by means of traffic management measures within the

existing infrastructure.

Figure 2-3 : Hourly link flow of the intersection

2.3 Pedestrian Movements

Pedestrian counts were conducted at four locations namely as shown in Table 3.3. Counts were done

at pedestrian crossings on the road within the area chosen for 12 hours. The summary of the

pedestrian analysis is given in the Appendix.

There are around 25,000 pedestrian crossings at the Boralesgamuwa Roundabout. Total crossings on

the Dehiwala-Maharagama Road are 13,750 pedestrians while on the Colombo-Horana road are

11,310 pedestrians. Maximum pedestrian flow takes place across the Maharagama Link at 5.30pm to

6.30pm which is around 700 pedestrians per hour (Figure 2-4).

0

500

1000

1500

2000

2500

3000

3500

4000

4500

6.30 7.30 8.30 9.30 10.30 11.30 12.30 13.30 14.30 15.30 16.30 17.30 18.30

Ho

url

y T

raff

ic F

low

Time

Hourly traffic flow on each road links of the intersection

B84 Road (Colombo Link)

B94 Road (Maharagama Link)

B84 Road (Piliyandala Link)

B94 Road (Dehiwala Link)


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Figure 2-4 : Total daily pedestrian movement at Boralesgamuwa roundabout

The Average Number of Pedestrians per hour crossing the road at those locations is summarized in

Table 2.2. The pedestrian demand for crossing the road seems to be somewhat constant ranging from

400 to 600 per hour with the highest flows observed on the Maharagama Link. However, these are

the pedestrian counts close to the marked pedestrian crossings and the total crossings within the study

area would be more than this.

According to these data, the average maximum flow rate of pedestrian crossings in one direction will

be 6-7 persons per minute. This could be easily handled with any phase arrangement of a signalized

intersection.

The bus stops in each direction of all road links are located after passing the intersection. Therefore,

bus passengers who are transferring from one direction to the other have to cross a road at least once.

It could be seen that both the vehicular peak and the pedestrian peak and the flow pattern during the

day is very similar (Figure 2-4 and Figure 2-5). This has aggravated the traffic congestion especially

during the peak periods at the intersection. There are above 10,600 vehicle movements and 2200

pedestrian crossings take place at the intersection during the evening peak hour. These figures are

10,200 and 1700 during the morning peak hour. Therefore, both vehicles and pedestrian movements

have to be considered for traffic management at the intersection.

Table 2-2: Peak Pedestrian Movements on Main Links

Location Maximum Hour Flow Time

Piliyandala link 419 5.30 – 6.30pm

Dehiwala Link 507 4.30 – 5.30pm

Kohuwela Link 623 4.30 – 5.30pm

Maharagama Link 727 5.30 – 6.30pm


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Figure 2-5: Hourly Pedestrian flows across each road links at the intersection

2.4 Speed and delay

The average speed at the roundabout is found to be 20km per hour according to two days average

travel time surveys (Table 2-3). This average is taken from 410 number of travel data obtained over

600m length covering all the turnings at the roundabout. The variation of speed shows that the

Piliyandala and Kohuwela approaches have the lowest speed. This varies between 8 to 25 km per hour

with right turns from Piliyandala approach to Maharagama in the am peak and through movements

from Kohuwela approach to Piliyandala in the pm peak also registering below 10 km per hour. The

speed variation on the Dehiwala-Maharagama road is between 14 km per hour to 28 km per hour. The

Kohuwela to Piliyandala approach has the largest variation ranging between 8 km per hour to 25 km

per hour, while right turns from Piliyandala to Maharagama has the lowest average ranging between 7

km per hour to 11 km per hour which also records the minimum average speed of 9km/hr. This

movement involves some congestion in Piliyandala link as well as the obstructions from the bus stop

towards Maharagama. The overall average vehicle speed is estimated at 24 km per hour.

0

100

200

300

400

500

600

700

6.3

0

7.3

0

8.3

0

9.3

0

10.3

0

11.3

0

12.3

0

13.3

0

14.3

0

15.3

0

16.3

0

17.3

0

To

tal P

ed

es

tria

n C

ros

sin

gs

Time

Total Hourly Distribution of Pedestrian Volumes By Links

Pliyandala Dehiwela Kohuwala Maharagama


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Table 2-3: Two days hourly average speed of each turning of the roundabout

2.5 Accident Studies

The accident statistics recorded by the Police for this study area for the year 2007 is given in Table 2-

4. It can be seen that there are around 7 fatal accidents and 19 grievous injury accidents per year at

this junction.

Table 2-4: Summary of Road Accidents in Study Area (Year 2007)

No

Road Section Accident Type

Total Road Name

From Where to

Where Length Fatal Grievous Light

Injuries

Property Damage

Only

1 B094 : To Maharagama

Within 300m of Junction

300 m 2 4 5 5 16

2 B094 : To Dehiwala


300 m 1 3 2 1 7

3 B084: To Piliyandala


300 m 1 6 8 4 19

4 B084 : To Kohuwala


300 m 3 4 9 4 20

5 In Junction 2 4 1 7

Total 7 19 28 15 69

Right Through Left Right Through Left Right Through Left Right Through Left

1 2 3 4 5 6 7 8 9 10 11 12

6.30 7 16 18 16 16 23 15 23 23 21 19 20

7.30 9 17 13 23 18 20 18 25 25 24 23 13

8.30 9 19 23 19 26 23 21 23 23 24 25 20

9.30 9 21 22 22 18 25 24 23 24 21 26 20

10.30 8 19 19 23 22 25 24 23 21 24 25 20

11.30 9 17 18 18 26 28 23 22 26 25 23 22

12.30 10 17 19 20 26 27 24 18 27 23 19 23

13.30 11 23 21 22 24 24 19 14 23 20 25 23

14.30 11 20 22 25 25 25 24 20 25 20 24 22

15.30 10 18 19 22 22 26 21 24 26 22 25 25

16.30 8 26 23 19 24 25 27 20 24 17 23 22

17.30 11 19 23 14 14 16 11 8 26 15 20 18

Minimum 7 16 13 14 14 16 11 8 21 15 19 13

Maximum 11 26 23 25 26 28 27 25 27 25 26 25

Avarege 9 19 20 20 22 24 21 20 24 21 23 21

Time

From

Average Speed (km/h) Over a Length of 600meters From the Direction of :

Piliyandala Dehiwala Kohuwala Maharagama


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2.6 Road Infrastructure

The road infrastructure within the study area is mainly the Colombo Horana Road and Dehiwala-

Maharagama Road. Abeyrathna Mawatha is one of the roads serving the residential areas from the

Horana Road and which also connects to the Dehiwala Road away from the junction. This road is

incapable as a bypass road in avoiding the junction, due to its capacity and length. There are no other

important roads falling within the study area.

At present, the Colombo–Horana Road (B84) carries an ADT of around 36,000 vehicles. It has 4 lanes

close to the junction at a length of around 100-200 meters to both sides from the junction. Beyond this

it has only two lanes for both directions of traffic. The ADT of around 21,000 vehicles carries on

Dehiwala – Maharagama Road (B94). It has two lanes undivided lane configuration throughout the

entire road lengths. Aberathna Mawtha is having two way single lane capacities and it has a right of

way of around 9.5 meters from wall to wall. Road link configuration of Boralesgamuwa roundabout is

given is Figure 2.3. The cross sectional dimensions of all road links approximately 60 meters away

from the junction (shown in Figure 2.6) is given in Table 2.5.

Figure 2-6: Road Link Configuration of Boralesgamuwa Roundabout


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Table 2-5: The cross sectional details of the road links in the study area.

All main road links at Boralesgamuwa have raised walkways which are not paved at the moment.

Therefore the surface is not even and pedestrians are often reluctant to use them. These walkways are

approximately 3m wide and occupied by parked three wheelers and motor bicycles. Pedestrian

crossings are available and marked across all four links in close proximity to the junction. There is

good use of these crossings as they are marked close to the junction.

Figure 2-7: Three Wheeler Parking Locations in the Study Area

The demand for parking of private vehicles and commercial vehicles could also be seen on either side

of the road very close to the junction. There are around 6 different three wheeler parks available

within a 200 meter radius on each of the links. These have a total capacity of over 100 stalls. All these

parking lots are however located on the pedestrian walkways. This causes pedestrians to use the road

way thus causing traffic congestion. The locations of these three wheeler parks are shown in Figure 2-

7. The number of parking slots in each of the respective parks is given in Table 2-6.

LaneWalkway/

ShoulderDrain

Gap to

Building

Edge

Total

(Wall to

Wall)

1 Colombo - Horana Road (Piliyandala Link) A-A 4 3.95 3 0.6 3.0 29.0

2 Colombo - Horana Road (Kohuwala Link) B-B 4 3.45 4 0.6 8.0 39.0

3 Dehiwala - Maharagama Road (Dehiwala Link) C-C 2 4.90 3 0.6 2.8 22.6

4 Dehiwala - Maharagama Road (Maharagama Link) D-D 2 5.60 3 0.6 1.5 21.4

Width of Road Sectional Elements (m)

Road Name and SectionItem

No

Map

Reference

No

#

Lanes


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Table 2-6: Details of Three Wheeler Parking in the Study Area

The location of important traffic attracting land use in the study area is shown in Figure 2-8. These are

given in Table 2-8. It can be seen that all these traffic attractors have main road frontages and are also

located very close to the junction. Also it is observed that the onsite parking provided is inadequate

for all these locations when compared to the demand for parking except at the Arpico Shopping

Centre (Table 2-7). Therefore, the additional parking at each of these traffic attractors always use the

left lane of the carriageway or walkways reducing important lane space close to the junction.

Figure 2-8: Locations of Important Land Use in the Study Area

1 Horana Road Link 1 60 28

2 Maharagama Road Link 2 25 15

3 Maharagama Road Link 3 20 32

4 Dehiwala Link 5 35 19

5 Horana Road Link 6 195 10

Total 104

Road Name and SectionItem

No

Map

Reference

No

Distance to Junction Centre (m) # Parking Lots


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Table 2-7: Details of the Important Land Use in the Study Area

2.6.1 Highway Geometry of the Study Area

Boralesgamuwa junction is an obliquely set out junction when considering the orientation of the four

approach links. The approach radius of the curvatures of each link is given in Table 2-8. According to

these values, it is required to have all such approaches to be super elevated even to maintain a speed

of 40 km/hr when approaching the junction. However since this is an intersection, the above criterion

is not applicable as speeds are expected to be reduced at the roundabout. The junction center has the

highest elevation in the longitudinal section of the Colombo-Horana Road in the study area and both

approaches climbs to this crest at a 3% gradient (Figure 2-10).

Table 2-8: Existing Geometric Properties of the Approach Links of the Intersection

1 Seylan Bank Horana Road Link 1 40 2

2 Cargills Super Market -Do- 2 30 2

3 Police Station Colombo Link 3 45 -

4 Laughs Super Market -Do- 4 105 10

5 Public Market Maharagama Road Link 5 20 -

6 People's bank -Do- 6 130 -

7 National Savings Bank (NSB) -Do- 7 130 -

8 Arpico Super Market -Do- 8 120 60

9 Hatton National Bank (HNB) -Do- 9 120 6

10 Sri Lanka Telecom (SLT) Horana Road Link 10 200 -

11 80

Land Use and Name

Total

Item No Road Name and SectionMap

Reference

No

Distance to

Junction

Centre (m)

Approximate #

Parking Lots

Available

1 Horana Link 200 40

2 Colombo Link 180 80

3 Dehiwala Link 120 30

4 Maharagama Link 80 40

Approximate Curve

Length (m)

Angle of Deviation at

intersection

10°

18°

Item

No

Approach Road Section to

Junction

Approach Radius of

Curvature (m)


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Figure 2-9 : Proposed Lane Arrangement of the Intersection.

Figure 2-10: Longitudinal Section along B84 Road at the Roundabout

2.7 Summary of Problems

The following is a summary of problems identified in this section:


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• The junction has both a horizontal and vertical curvature.

• There are no sidewalks on most of the approaches to the junction.

• Some sections where there are sidewalks there are trade stall and kiosks obstructing the

movement of pedestrians.

• Pedestrians mostly use either the unpaved shoulder weaving in between parked vehicles and

kiosks or the road carriageway.

• There are over 100 dedicated three wheeler parking stalls in 6 parking lots located within the

200 metres distance from the junction which are located in a manner where they obstruct

pedestrian walkways.

• The overall average speed through the Boralesgamuwa town and passing the junction is 24

km per hour. The Piliyandala approach and Kohuwela approach in the am and pm peak

register unacceptable speeds of less than 10 km per hour. The right turns from Piliyandala to

Maharagama are also mostly less than 10 km per hour throughout the day.

• The road right of way widths vary for each approach. In the case of the Dehiwala –

Maharagama road, it is between 21 to 23 metres and has 3 lane width which function as a two

lane highway with parking on both sides. In the case of the Piliyandala approach the width is

29 metres, but still provides for 3 lanes with broad shoulders which accommodate parking as

well as temporary structures at intermittent places. The widest approach is the Kohuwela

approach which has 39 metres right of way which has 4 lanes and space for parking.

• The ADT of the Colombo-Horana Road (B084) is around 35,000 while that of Dehiwala –

Maharagama Road ( B094) is around 29,000.

• There are around 25,000 pedestrian movements across the junction during the day. The

average flow rate is around 2,000 per hour with the highest across the Dehiwala and

Maharagama approaches. Most of these pedestrian crossings especially in the peak periods

are from transfer of bus passengers between Route 119 (Dehiwala-Maharagama) and buses on

the Colombo-Horana Road. The bus stops are located in the far-side so that pedestrian

crossings are maximized in transfers.

• The am peak hour load at the junction is 10,200 vehicle movements and 1700 pedestrian

movements. The pm peak load is 10,600 vehicle movements and 2200 pedestrian movements.

• There are 7 fatal accidents recorded for year 2007 at the Boralesgamuwa junction. Total

accidents recorded are 69. The major conflicts have arisen as a result of pedestrian and


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vehicle conflict. Hence this should be a major concern as 7 fatal accidents for a junction of

this nature has to be considered excessive when compared to other junctions being studied.

• The major problem at this junction is the lack of traffic management of the approaches. This

results in loss of road capacity as well as in increasing of road accidents.


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CHAPTER 3 - PROPOSED SOLUTIONS

The following interventions are required for the problems identified in the earlier chapter.

• Junction Control

• Access Control close to the junction

• On Street Parking controls

• Provision of segregated pedestrian facilities

• Geometric improvement to the intersection

• Design and allocation for bus stop and bus bays

• Re routing of buses

3.1 Junction Control

There is a proposal to consider a flyover at the junction. The alternative to this would be signalization

of the junction since roundabout capacity will be inadequate.

The total ADT of the Boralesgamuwa roundabout is above 53,000 at the moment. The growth rate of

traffic at this roundabout from last year to this year is 6.7%. This is generally a high growth rate.

Since a roundabout is a viable solution when there is a higher fraction of right turns, the present

junction management with a roundabout does not seem to be a suitable solution, when through

movements dominate due to the new improvements of the B084 and B094 roads (Table 3-1).

Table 3-1: Split of total vehicle turns at Boralesgamuwa Roundabout

3.1.1 Flyover Option

A flyover option of the Colombo Horana road above the Dehiwala- Maharagama road will facilitate

improved through movement for around 26,821 motorized vehicles on the Colombo-Horana Road.

Since there are 1,660 bus movements on the Colombo-Horana road, the total flyover users will be

25,160 motorized vehicles. The total motorized through traffic on the Dehiwala Maharagama road is

around 11,000 vehicles. Therefore, according to the traffic level, a flyover along the Colombo Horana

road will be more feasible than on the Dehiwala Maharagama road. With a 12% peak period demand,

the flyover should be able to provide a capacity of 3,020 vehicles per hour. Thus a 2-lane flyover with

an observed peak period directional split of 55/45 will require a peak period peak direction capacity of

1,660 vehicles per hour. If the flyover is designed as a two lane undivided road with 4-5% grade, the

2007 2008

Left 20 14

Through 63 71

Right 17 15

% Total Turning Movement Turn


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capacity available will be around 2,000 vehicles per hour. This will clearly be inadequate and delays

will occur due to queuing of vehicles. Moreover, slow moving vehicles climbing the flyover will be

very slow. This will cause queuing to take place behind such vehicles. With a 55/45 observed spilt

during peak period, this will become very severe due to the lack of passing opportunities as opposing

flow will also be high. Thus a 4 lane flyover will be required to adequately address the capacity issue.

Since the nature of existing vertical alignment of the Colombo Horana Road is such that it has the

crest of a vertical curve at the roundabout itself the flyover length has to be increased from a

minimum (280m) to 475m as shown in Figure 3-1. This length is calculated according to the gradient

of both approaches shown in same figure.

Figure 3-1: Vertical Alignment of the flyover along Colombo-Horana Road (B084)

3.1.1.1 Flyover Option 1- Concrete Only

There are two options available for flyover construction based on the method and material used for

the construction. Since the Colombo- Horana Road selected in the study area has some curvatures in

its horizontal alignment along the centre line, the same alignment could be followed by the flyover in

order to reduce the damage to the buildings and to cause minimum acquisition. This option is shown

in Figure 3-2. The flyover length will be 475 meters and the effective length including the horizontal

approach length, will be around 600 meters. However, in this case the flyover should be constructed

as a concrete structure (as Ragama Concrete Flyover) to obtain the required curvature.

Since this can be constructed as a cantilever concrete structure with single pier at the centre,

acquisition in between the road section of the two ramps are not involved as the access roads can be

accommodated under the bridge. Therefore there will not be considerable damage to the buildings

besides the existing Colombo Horana Road. Also since the construction of piers is confined to the


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road centre, traffic during the construction is minimal. Therefore these are very significant advantages

over steel flyovers which need wider concrete foundations projecting 1.5m height above the road

surface (Kelaniya Steel Flyover).

Figure 3-2: Horizontal Alignment of Flyover along B84 Road with existing Road Layout

(Cantilever Bridge).

3.1.1.2 Flyover Option 2 – Steel

Generally the steel flyovers are difficult to construct as they use pre- cast sections and curves are

difficult to provide for. Hence a possible horizontal layout of a straight flyover across the junction is

shown in Figure 3-3. The acquisition of land and demolition of buildings has alternatively shifted

from one side to the other side along the length of the flyover as shown in this figure.


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Figure 3-3: Horizontal Alignment of the Flyover along the Colombo Horana Road with a

Straight Segment.

Since both options for flyovers have to be span long distances (475m) due to the increased vertical

displacement required the cost of the construction will be very high. Furthermore a 4 lane flyover will

require a width of around 18 metres therefore the resulting acquisition will be quite severe with the

road width required at the base of the flyover having to have a right of way width of at least 34

metres. This means that in the Piliyandala approach around 5 metres width has to be acquired.

Acquisition from the Kohuwela approach will be less.

A distinct advantage of having a flyover would be the creation of space under the bridge. While

unused space would be a problem, development for commercial purposes would also create additional

traffic issues. The most suitable use of this space would be for parking of vehicles. On a 475 m length

of flyover it is possible to accommodate parking for around 100 vehicles. However the type of bridge

and the type of design utilized has to be given due consideration to facilitate this. If columns are

located on the extremes as opposed to the centre then the remaining lane will be constrained and some

acquisition may be necessary to ensure that at least 2 lanes of traffic run right through on the ground.

Moreover if the horizontal structural elements are placed at the bottom of the bridge as in the case of a

steel structure, then they will obstruct the through movements. If a steel bridge is constructed like at

Kelaniya, the space under the bridge will become marginalized space and become useful for small

shops and informal traders thus reducing the mobility for turning traffic. This may be addressed by

considering a concrete bridge which can be designed with adequate clearance for parking of vehicles

and for turning movements of the traffic at grade under the bridge.


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3.1.1.3 Impact of Flyover on Urban Landscape

Boralesgamuwa is a significant urban node on the way to the south of Colombo. It is the last such

node that occurs in quick succession on the Colombo-Horana road. Hence, today this has become a

passer-by urban space rather than a node. Boralesgamuwa is also a busy place where many people

transit, shop, and use as their town centre. However, due to heavy unplanned traffic the container

quality of this urban space has deteriorated. Therefore, any effort to ease out the traffic shall

strengthen the livability of the town centre.

This urban centre does not have any particular significant urban character but the majority of land

utilization is for mid-scale commercial purposes The most notable physical character is the slight

climb on both the roads where they meet, therefore the roundabout is at a higher level. This existing

character could be responded by new constructions, thus rebuilding the urban centre as a true urban

space which would facilitate life.

In easing out the traffic, the authorities will have to take necessary steps to scale down the domination

of the traffic artillery and allow the domination of public space. By scaling down the dominance of

the roads, one can support urban life, thus turning Boralesgamuwa into a typical mid-scale town

centre. There shall be more spaces for citizens and those who transit, so that they will respond to the

urban spaces more positively. Those who cross the city centre would also enjoy the strengthened

urban images. These steps shall empty through traffic as quickly as possible, without hindering the

accessibility to urban spaces and buildings.

We do not consider a flyover as a socially-viable and architecturally-suitable solution for many

reasons. This heavy bulky structure will further strengthen the dominance of traffic, completely

ignoring the humane quality of the urban space. The above mentioned climb of the roads means the

flyover will have be rather high, thus over-stating its presence. This one-sided engineering solution

will further deteriorate the use of urban space by its citizens. The flyover will also dissect the city into

two major sections thus completely diluting the container quality of the city and degrading into a

leftover ghetto like space. The passer-by nature of Boralesgamuwa will further be reinforced, and the

city centre would face a gradual extinction. The sprawl will also continue thus stretching the traffic

congestion further down the two roads. The citizens, having lost accessibility to their urban spaces,

will lose the connection to their living city.

Also there will be a large extent of unused land under the flyover due to this long span. Also due to

this long length, the entire town area will be separated and the service road network may not be

attractive enough to through travel users even though they really need to stop at this town center for a

service. There may be an effect on the local economy since the town centre is confined to the entire

length of the proposed flyover.

3.1.2 Signalization

Signalization of the existing roundabout is also a possible option. The percentage of right and left

turning movements at Boralesgamuwa is generally in equal proportion to each other in all approaches


3-6 | P a g e


with the major flow in the through direction. Therefore signalization is a favorable option as a short

and medium term solution for the congestion here.

Figure 3-4: Road sections to be improved under signalization of the intersection.

The lane arrangement for signalization of Boralesgamuwa intersection is shown in Figure 3-5. In

order to provide adequate capacity for at least 10 years, the design capacity should be considered as

95,000 ADT. Accordingly the requirement would be for 6 lanes on the Colombo-Horana Road and 4

Lanes on the Dehiwala-Maharagama Road at the intersection. All links should be divided with a 1.5m

wide center median in order to prevent crossings and “U Turns” close to the intersection. Separate

Left lane filter should be provided from the Piliyandala Link to the Dehiwala Link and form the

Dehiwala Link to the Colombo Link. This can be provided with the space presently available.


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Figure 3-5: Lane Arrangement of the Intersection for Signalization

3.1.2.1 Phase arrangement of the signal design

Left turns from Piliyandala and Dehiwala approaches at the proposed signalized intersection are

provided with a separate turning lane. Separate right turns are provided from the Colombo Horana

Road. Right turns are shared with through movements at the two approaches of the Dehiwala

Maharagama Road. However the discharge capacity can be made available with the three phase

arrangement without much difficulty. The signal design will be successful for a 3 phase arrangement

and the signal timings were calculated for the above lane arrangement. The cycle time of the phase

arrangement could be kept as 90 seconds most of the time of the day. It could be kept at even 60

seconds at off peak periods (10.00 am – 1.00pm and 3.00pm – 4.30pm). However it reaches 180

seconds during the two peak periods. The intersection delay with this arrangement is estimated as

1,362,115 vehicle seconds (378 vehicle hours) during the 12 hour traffic period of a working day.

Therefore this delay should be compared with the existing delay due to various activities of

obstructions close to the intersection.


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Figure 3-6: Signal Timing for Boralesgamuwa

3.2 Traffic Management Measures

The signalization of the intersection also requires parallel improvements to some of the supporting

infrastructure such as parking control and management, pedestrian control, bus parking and bus

routing through the junction. If such facilities are also provided together with signalization, the

benefits will be maximized since they will achieve both traffic flow speed improvements and reduce

accidents.

These facilities are considered necessary for a length of around 700 meters along the Colombo Horana

Road and 400 meters along the Dehiwala –Maharagama Road.

The specific improvements and suggestions to complement the signalization of the junction are

discussed below:

• On Street Parking controls

• Access Control close to the junction

• Provision of segregated pedestrian facilities

• Geometric improvement to the intersection

• Design and allocation for bus stop and bus bays

• Re routing of buses

0

20

40

60

80

100

120

140

160

180

200

00.0

…

01.0

…

02.0

…

03.0

…

04.0

…

05.0

…

06.0

…

07.0

…

08.0

…

09.0

…

10.0

…

11.0

…

12.0

…

13.0

…

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…

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23.0

…

Sig

nal C

ycle

Tim

e

Time of the Day

Adjusted Cycle Time with Three Phase Signal System at Boralesgamuwa

Monday


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3.2.1 Parking Control

It is suggested that private and commercial parking should be controlled by means of specifying the

“parking areas” and “no parking” areas. In this respect parking bays could be constructed beyond the

queue formation length of the junction which would be around 75 metres in the upstream direction as

well as beyond 25 metres of the downstream direction. This will allow maximum storage of vehicles

up stream prior to discharge from the signal on green light. It will also allow parking after left turning

vehicles have merged with the traffic. This would be adequate as left turns will only share with right

turns of the opposing traffic and excess capacity will be available for merging traffic to the

downstream over a length of 25 meters.

It is also recommended that:

• Demarcation on the road with durable road paints, and use sign boards

• On street parking in the peak direction should be banned within 200m to intersection

Special consideration should be given to parking requirements of 3 wheelers. Some of these bays

could be allocated for 3 wheelers.

3.2.2 Access Control

At present most business establishments located within very close proximity to the junction have un-

restricted access to the road there by disturbing the flow of traffic not only with vehicular movements

but also by parking vehicles in such places where a part of the vehicle protrudes to the road. It is

recommended that guard rails be erected up to at least 75 metres on either side of the junction on each

of the approaches. Only limited access should be provided to commercial establishments. This will

also help the movement of pedestrians and improve safety as well.

3.2.3 Segregated pedestrian facilities

It was noted that the pedestrian activity level at Boralesgamuwa is as important as the traffic

movements. Therefore some degree of priority should be placed on the requirements of pedestrians

within the study area. This can be identified as follows:

• Inclusion of signalized pedestrian crossings within the signalization of the intersection.

• Provide at least another crossing at a distance of 75 metres to the junction with a centre

median refuge.

• Construct a centre median barrier so that pedestrians would not cross the road in between the

crossings.

• Provide raised and paved sidewalks up to end of the built up areas on all approaches. This

will be around 1,000 metres in all. At least the first 75 metres should have guard rails on

either side.


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• Remove the unauthorized and authorized constructions including lottery kiosks, utility poles

and even sign posts that are constructing pedestrian flow.

These measures will prevent pedestrians crossing at unsafe locations as well as prevent them from

getting in to the path of motorized traffic thus improving safety for pedestrians as well as speed of

vehicles.

3.2.4 Geometric improvements to the intersection

The Boralesgamuwa junction as has been pointed out in earlier chapters is located at a top of a

vertical curve. It is also located within a horizontal curve on the Colombo Horana Road. There are

some geometric improvements that are required especially for the Piliyandala Link of Colombo

Horana Road. This could be accommodated within the existing Right of Way junction where the road

could be re-aligned to reduce the horizontal curvature.

In doing this the entire available road should be utilized for street space, with broad side walks. The

temporary building projections and unauthorized activities that are common especially along the

Piliyandala Link should be removed. It is also recommended that the geometry of the lanes around the

junction should include lane markings and marking of parking stalls as well as bus halts.

3.2.5 Location and Design of bus stops and bus bays

There are over 2,600 bus movements through the junction every day. Almost all buses make at least

one stop within the study area. At present all bus stops are located at the far side of the junction (i.e.

passing the junction) so that transfer passengers have to cross one stream of traffic thus causing

intense congestion due to the pedestrian movements across the peak traffic flows.

Most bus to bus transfers occur from the Colombo Bound buses to the Maharagama bound buses in

the am peak and the reverse in the pm peak is from Dehiwala Bound buses to Horana bound buses.

Hence it would be most efficient and safe for the bus stops to be located as follows:

• Horana Direction – far side

• Colombo Direction – far side

• Dehiwala Direction – near side

• Maharagama Direction – near side

3.2.6 Re-routing of buses

Although beyond the purview of the RDA, one of the solutions to the traffic problem caused by high

stoppage of buses at halts and the subsequent flow of pedestrians across the roads is to introduce some

bus routes that would make right turns and left turns thus taking passengers without transferring them

as the junction. In this respect the following routes may be considered:


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• Piliyandala – Battaramulla via Boralesgamuwa, Maharagama, Pamunuwa and

Jayewardenepura Hospital

• Kesbewa – Fort via Boralesgamuwa, Karagampitiya, Kalubowila Road, Galle Road and

Bambalapitiya

• Maharagama – Fort via Boralesgamuwa, Kohuwela, Pamankade, Galle Road and

Bambalapitiya


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CHAPTER 4 - ECONOMIC ANALYSIS

4.1 Costs

The cost of the improvements proposed in the above chapter will include the following

• Signalization of the intersection including acquisition

• Access Control around the intersection.

• Widening and Improvements to the approach roads, realignment, construction of signs and

road markings.

The following general works are also recommended.

• Improvements to carriageway and resurfacing of approach roads up to intersection.

• Reconstruction and improvements to walkways on the above sections

• Improvements to the Traffic Management measures in the study area including access control,

guard rails, bus stop relocation, construction of bus bays etc.

The construction cost for each option is given in Table 4-1.


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Table 4-1: Comparative Cost Estimate of Options in 2008 prices

4.2 Benefits

Economics benefits from this project are many fold. For the purpose of this study we will include the

following benefits:

• Reduction in Vehicle Operating Costs for vehicles using Horana Road and Dehiwala -

Maharagama Road

• Value of Travel Time Savings for vehicles on Horana Road and Dehiwala -Maharagama

Road

• Saving from Reduction of Accidents

4.2.1 Traffic Analysis

In computing the above benefits the traffic analysis has considered the following.

Qty Amount (Rs) Qty Amount (Rs)

1.0 Land Acquisition, & Demolision and Reconstruction

1.1 Road Length m 700 475

1.2 Single Storey m2 40000 1035 41,400,000.00 2600 104,000,000.00

1.3 Two Storey m2 100000 60 6,000,000.00 560 56,000,000.00

1.4 Three Storey m2 160000 27 4,320,000.00 380 60,800,000.00

1.5 Total Land m2 30000 1122 33,660,000.00 3540 106,200,000.00

Sub Total 1 85,380,000.00 327,000,000.00

2.0 General Civil Cost

2.1 Preliminaries Sum 5,000,000.00 10,000,000.00

2.2 Clearing m2 80 4800 384,000.00 4370 349,600.00

2.3 Base & Sub Base m2 850 4800 4,080,000.00 7400 6,290,000.00

2.4 Asphalt Surfacing m2 2,300 14940 34,362,000.00 7400 17,020,000.00

2.5 Walk Ways m2 900 8400 7,560,000.00 3000 2,700,000.00

2.6 Kerbs m 1,450 8400 12,180,000.00 2000 2,900,000.00

2.7 Drains m 4,600 2800 12,880,000.00 1000 4,600,000.00

2.8 Fencing and Barricades m 14,000 960 13,440,000.00 100 1,400,000.00

2.9 Road Markings m 90 6660 599,400.00 1300 117,000.00

2.10 Sign Boards Nos 35,000 58 2,030,000.00 20 700,000.00

2.11 Traffic Signal Unit Nos 6,000,000 1 6,000,000.00

Sub Total 2 98,515,400.00 46,076,600.00

3.0 Cost of Flyover (4 Lane) m 6,076,389 475 2,886,284,722.2

Total 183,895,400.00 3,259,361,322.22

Add for Variations (20%) 36,779,080.00 651,872,264.44

Grand Total 220,674,480.00 3,911,233,586.67

Ite

m N

o

Item Description Unit Rate (Rs)

Option 1 Option 2

Signalization of intersection Flyover with Streight Ramp


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The present travel speeds reported in Chapter 3 can be summarized as follows:

• Horana Road Through Traffic – 19 km/hr

• Horana Road Turning Traffic – 19 km/hr

• Dehiwala-Maharagama all traffic – 22 km/hr

The two options considered along with the other traffic management measures that have been

recommended will improve the speeds of these two flow movements in particular. The increase in

speed of the left and right turns on both roads are given below in table 4.2

Table 4-2 : Comparison of Speed ‘Before and After’

Approach Turn Speed Km/hr

Existing Signalization Flyover

Piliyandala Left 20

25 km/hr

25

Through 19 35

Right 9 25

Dehiwala Left 24

30

Through 22

Right 20

Colombo Left 24 25

Through 20 25

Right 21 25

Maharagama Left 21

30 Through 23

Right 21

The signalization delay for the 3 phase arrangement was estimated at 1,362,115 vehicle seconds. This

works out to around 27 seconds per vehicle. When adjusted for the average speed gain it translates to

the improvement of the junction speeds up to 24.7 km/hr, which we shall assume as 25 km/hr.

In the flyover option, it was shown in Section 4.1 that the estimated average demand would be around

26,800 vehicles per day, with an average flow rate of 450 vehicles per lane per hour. After adjusting

for capacity reduction factors with respect to lane width, gradient and heavy vehicles (and low horse

powered vehicles) we get a volume to capacity ratio of 0.3 which translates to average speeds of

around 40 km per hour for a maximum speed limit of 50 km/hr and free flow speed of 70 km/hr.

However, low horse powered vehicles such as three wheelers, and some motor cycles as well as heavy

vehicles such as trucks and buses are unlikely to attain this speed especially on the gradient. Since

these vehicles constitute nearly 50% of the flow, the average speed may have to be considered as 35

km/hr for the flyover. With respect to the turning movements we will assume it will increase up to 25

km/hr and for the Dehiwala-Maharagama road all movements will increase to 30 km/hr.


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4.2.2 Economic Benefits

Table 4-3 and Table 4-4 show the computation of economic costs and benefits for the signalization

and flyover options respectively. The calculations are based on a ‘before and after’ traffic flow

estimate taking into account the flow estimates given in Section 5.2.1 for private vehicles, goods

vehicles and buses separately. The cost estimation uses unit values from ‘Assessing Public Investment

in the Transport Sector’2. These include vehicle operating costs at given speeds wherein the roughness

was assumed at IRR =3. The Value of Time for passengers was taken after considering Vehicle

Occupancy Rates (VOR) and the Value of Time (VoT) from the above reference after adjusting for

price escalation using CCPI. All estimates shown in Table 4-3 and Table 4-4 are in SLR in 2008

prices.

Accident savings are computed assuming that 50% of the accidents presently occurring at the

Boralesgamuwa junction study area could be reduced by a fly over with signalization option reducing

by 40% since both options which will separate many conflicts and make it safer for both pedestrians

as well as vehicle users. The economic cost of accidents also has been taken from the same source.3

2 National Planning Department, Authored by Kumarage A.S., Ed Storm, T.L. Gunaruwan et al, 1999

3 Ibid


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Table 4-3: Economic Analysis for Signalization Option


4-6 | P a g e


Table 4-4: Economic Analysis for Flyover Option

length speed Ann. Cost

Private Bus Truck Total km km/hr Private Bus Truck Rs Mn

Section

Horana Road (Through Traffic) 19,460 1,741 2,267 23,468 0.6 19 29.55 59.4 54.36 168.4

Dehiwala-Maharagama Road 17,089 792 1,952 19,833 0.6 22 28.47 45.24 50.91 130.6

298.9

Travel Time Costs



Approach

Horana Road (Through Traffic) 19,460 1,741 2,267 23,468 0.6 19 204 1116.9 65.4

Dehiwala-Maharagama Road 17,089 792 1,952 19,833 0.6 22 204 1116.9 41.7

107.1

VOR VOT

Private 1.2 170

Bus 30 1116.9

SCENARIO WITH IMPROVEMENTS

Vehicle Operating Cost



Approach


Dehiwala-Maharagama Road 17,089 792 1,952 19,833 0.6 25 27.63 46.68 46.47 126.0

278.1

Travel Time Costs



Approach


Dehiwala-Maharagama Road 17,089 792 1,952 19,833 0.6 25 204 1116.9 36.7

86.4

ADT VOT(Rs/hr)

VOC(Rs/km)

ADT VOT(Rs/hr)

ADT VOC(Rs/km)

ADT (Average)


4-7 | P a g e


PRESENT SCENARIO-2008




Section


Horana Road (Turning Traffic) 8,541 47 838 9,426 0.6 19 29.55 59.4 54.36 63.2

Dehiwala-Maharagama Road 17089 792 1952 19833 0.6 22 28.47 45.24 50.91 130.6

362.1

Travel Time Costs



Approach


Horana Road (Turning Traffic) 8,541 47 838 9,426 0.6 19 204 1116.9 19.8

Dehiwala-Maharagama Road 17089 792 1952 19833 0.6 22 204 1116.9 41.7

126.9

VOR VOT

Private 1.2 170

Bus 30 1116.9

SCENARIO WITH IMPROVEMENTS




Approach


Horana Road (Turning Traffic) 8,541 47 838 9,426 0.6 25 27.63 46.68 46.47 58.2

Dehiwala-Maharagama Road 17089 792 1952 19833 0.6 30 26.7 45.24 46.47 122.4

321.5

Travel Time Costs



Approach


Horana Road (Turning Traffic) 8,541 47 838 9,426 0.6 25 204 1116.9 15.1

Dehiwala-Maharagama Road 17089 792 1952 19833 0.6 30 204 1116.9 30.6

87.1

ADT VOC(Rs/km)

ADT (Average) VOC(Rs/km)

ADT VOT(Rs/hr)

ADT VOC(Rs/km)


4-8 | P a g e


4.3 Cost-Benefit Analysis

The benefits computed in Tables 4-3 and 4-4 are as follows:

• Savings in Travel Time Costs

• Savings in Vehicle Operating Costs

• Savings in Accident Costs

In the case of economic benefits due to generated traffic, no increase in the economic activity of the

area has been assumed since the project is of a very local nature and unlikely to generate regional

development. Based on the estimates in Table 4-3 and Table 4-4, an economic analysis has been

performed to obtain the Economic Internal Rate of Revenue (EIRR). This is shown in Table 4-5 and

Table 4-6 for the signalization and flyover options respectively.

This analysis is based on:

1. The assumption that value of vehicle operating costs, travel time and maintenance costs will

increase but in a manner that they will remain constant in real terms over the project life.

2. Project Life for the signalization is taken as 10 years after commissioning, and for the flyover

option it is taken as 20 years, where construction is expected to be completed by end of 2010.

3. Traffic growth has been assumed at a very conservative 3% growth rate. This is much less

than the 4 to 6 percent growth seen in urban areas.

The following conclusions can be reached from this economic analysis:

4.3.1 Signalization Option

The summary of the costs and benefits that have been discussed in earlier sections have been

summarized and discounted over the project life in Table 4-5.

Based on the Table 4-5 it is seen that the Signalization Option the following conclusions can be

reached:

1. On the above assumptions it returns an EIRR of 19.7% which can be termed a moderate

return on investment for an urban road project.

2. At a discount rate of 0% it returns a Net Present Value of Rs 422 million over 10 years.

3. At undiscounted prices it returns a Benefit to Cost Ratio of 2.4.


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Table 4-5: Cost Benefit Analysis for Signalization Option

Year Cost Benefit

Capital Recurrent VOC VOT Accidents Generated Total Net

2008 0 0

2009 221

2010 4.5 21 21 19 0 60.1 56

2011 4.5 21 21 19 0 61.9 57

2012 4.5 22 22 20 0 63.8 59

2013 4.6 23 23 20 0 65.7 61

2014 4.6 23 23 21 0 67.7 63

2015 4.7 24 24 22 0 69.7 65

2016 4.7 25 25 22 0 71.8 67

2017 4.8 26 25 23 0 73.9 69

2018 4.8 26 26 24 0 76.2 71

2019 4.9 27 27 24 0 78.4 74

267.3 689.3 643

Total

Discount Rate 0.0

Generated Traffic 0.0

NPV 421.9 Rs Million

The following sensitivity tests have been also performed:

1. If construction costs increase by 50% in real terms the project returns an EIRR of 12.1%

which shows that the signalization project is not robust to absorb cost variations.

2. If benefits reduce by half over the project life period, returns an EIRR of 5.4% showing it is

marginally robust to absorb reduction in benefits.

4.3.2 Flyover Option

The summary of the costs and benefits that have been discussed in earlier sections have been

summarized and discounted over the project life in Table 4-6.

Based on the Table 4-6 it is seen that the Flyover Option the following conclusions can be reached:

1. On the above assumptions it returns a negative EIRR which does not indicate that the project

is economically viable.

2. At a discount rate of 0% it returns a Net Present Value of negative Rs 2,852million.

At undiscounted prices it returns a Benefit to Cost Ratio of only 0.2.


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Table 4-6: Cost Benefit Analysis for Flyover Option

Year Cost Benefit

Capital Recurrent VOC VOT Accidents Generate

d

Total Net

2008 0 0

2009 3,911 -3,911

2010 79.0 41 40 24 0 104.2 25

2011 79.8 42 41 24 0 107.3 27

2012 80.6 43 42 25 0 110.5 30

2013 81.4 44 44 26 0 113.8 32

2014 82.2 46 45 27 0 117.2 35

2015 83.0 47 46 28 0 120.7 38

2016 83.9 48 48 28 0 124.4 41

2017 84.7 50 49 29 0 128.1 43

2018 85.5 51 50 30 0 131.9 46

2019 86.4 53 52 31 0 135.9 49

2020 87.3 54 54 32 0 140.0 53

2021 88.1 56 55 33 0 144.2 56

2022 89.0 58 57 34 0 148.5 59

2023 89.9 60 59 35 0 153.0 63

2024 90.8 61 60 36 0 157.5 67

2025 91.7 63 62 37 0 162.3 71

2026 92.6 65 64 38 0 167.1 74

2027 93.6 67 66 39 0 172.1 79

2028 94.5 69 68 40 0 177.3 83

2029 95.4 71 70 42 0 182.6 87

5650.5 2798.6 1,059

Total

Discount Rate 0.0

Generated Traffic 0.0

NPV -2851.9 Rs Million

B/C 0.2

4.4 Non-Quantifiable Benefits

There are several other benefits that have not been included in the economic analysis which will

greatly favour the construction of the signalization project. These may be identified as:

1. Introduction of modernization to Boralesgamuwa city centre

2. Improvement to important National Highway.

3. Improves the bus to bus transfers.

4. Benefits to pedestrians in terms of time savings have not been computed.


5-1 | P a g e


CHAPTER 5 - CONCLUSIONS

The following conclusions on the above analysis based on the primary option of flyover versus the

signalization can be tabulated as follows:

Feature of Impact Signalization Option Flyover Option

Cost of Construction Rs 211 million for a 3 phase

signal with widening for 4 lane

approaches on Horana Road and

3 lanes at Dehiwala-

Maharagama road approaches.

Rs 3,911 million for a 2 x 2 lane

flyover of 475 metres

Urban Landscape No adverse Impact Considered too dominant for a

small suburban town centre

such as Borelesgamuwa.

Cost of Other General

Improvements

Included in above Included in above

Increase in Travel Speed Through traffic speeds on

Horana Road will increase from

19 km per hour to 25 km per

hour

Overall junction speed will

increase from and average of

around 22 km per hour to 25 km

per hour.

Acquisition Will require acquisition close to

the junction

Will require acquisition at the

toes.

Economic Benefit-Cost

Analysis

EIRR is 19.7% and NPV is Rs

422 million with a Benefit-Cost

ratio of 2.4.

NPV at 0% discount rate is

negative Rs 2,951 million and

the Benefit-Cost Ratio is 2.2.

Safety Will improve both at

intersections and by placing

centre median guard rails.

Estimated 40% reduction.

Will improve due to grade

separation. Estimated 50%

reduction.

Level of Service Signal Timing for existing flow

returns an acceptable Level of

Service

Width is inadequate for

acceptable Level of Service on

two lane undivided flyover.

Ramp gradient may have to be

restricted to 4%.

Adequacy of Capacity Will be adequate for next 10

years and up to 20 years if

public transport is improved

Two lane undivided flyover will

not be adequate for more than 5

years. Four lanes will be

adequate for over 20 years.


5-2 | P a g e


Feature of Impact Signalization Option Flyover Option

Delays during Construction Relatively small as construction

duration will also be very short

Heavy since the construction

length is high and centre median

piers have to be constructed.

There are no roads adequate for

by pass. Heavy congestion will

prevail.

Bus Operations from

Terminals

Need Improvements. Re routing

is suggested.

Needs Improvements. Re

routing is suggested.

Bus Stopping Bus stops on Dehiwala-

Maharagama Road have to be

brought to near side (before the

junction.

Bus stops on Dehiwala-

Maharagama Road have to be

brought to near side (before the

junction.

Pedestrian Facilities Required as identified

Parking Facilities Off Street parking facilities

required especially for 3

Wheelers

Some parking can be

accommodated under the

flyover.

This analysis clearly shows that the signalization option is viable as against the flyover.


6-1 | P a g e


CHAPTER 6 - RECOMMENDATION

The following measure to improve the traffic flow in Boralesgamuwa Junction can be recommended

based on the economic viability and other issues discussed earlier.

• Junction Control using signalization. This will require widening of the approach roads to

include geometry of 6 lanes on the Colombo-Horana Road and 4 lanes on the Dehiwala-

Maharagama Road.

• Access Control close to the junction by constructing guard rails with limited openings to

prevent vehicles parking obstructing the flow of traffic at the intersection as well as to reduce

disruption to free flow caused by vehicles entering and exiting the different establishments at

the junction.

• On Street Parking controls in the form of designating ‘no parking’ areas and creating parking

bays for 3 wheelers at properly designed and located places.

• Provision of segregated pedestrian facilities with raised sidewalks along both roads with

pedestrian crossings located not further than 75 metres apart from each other with centre

median refuges.

• Relocate bus stops on Dehiwala – Maharagama Road and to construct proper bus bays on all

approaches.

• Re routing of through buses to reduce transfers at the Boralesgamuwa junction and adding to

congestion caused by heavy pedestrian flows.

These measures will result in

• Improved average speed on within Boralesgamuwa Study area from the exiting average of 22

km per hour to an estimated 25 km/hr.

• It will also lead to reduction of accidents as intersections are better controlled and pedestrian

crossings are better managed.

• There will be some modernization to the city.

The project is estimated to cost around 211 million rupees but its benefits will far outweigh the costs

in terms of an EIRR of 19.7% and an NPV at 0% discount rate of Rs 442 million and a Benefit-Cost

ratio of 2.4.

The project will remain moderately stable even if there are unexpected cost variations or reduction of

benefits.


6-2 | P a g e


In contrast a flyover of 475 metres will cost Rs 3,911 million. Such a project does not return the scale

of benefits to make it viable. The NPV is found to be negative.

The summary of the recommendations is shown in the Figure 6-1.

Figure 6-1: Map of Boralesgamuwa Study Area showing recommended improvements

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