TRB Transportation Applications Conference Congestion-Free Freeways US Department of Transportation ...

TRB Transportation Applications Conference

Congestion-Free Freeways

US Department of Transportation

www.fightgridlocknow.gov

Establishing a Metropolitan Network of Congestion-Free Freeways

Eliminating Freeway Bottlenecks in the Short-Term Without Major Construction

Patrick DeCorla-Souza

Federal Highway Administration


May, 2007





Overview

• The freeway congestion dilemma

• Addressing traffic flow breakdown with a new approach to transportation system operation

• Costs, revenues and benefits





As Much as Half of Freeway Capacity is Wasted in Rush Hours

SR 91 Express Toll Lanes:

• Vehicle throughput is double in the peak hour

• Free-flow speed vs. 15-20 mph in free lanes

0

200

400

600

800

1,000

1,200

1,400

1,600

Express Free

Vehiclesper hourper lane





Eastbound I-66, Northern VA – Monday Morning, March 5, 2007

5:00 a.m.

6:00 a.m.

8:00 a.m.

9:00 a.m. 7:00 a.m.

Outside Capital Beltway





Travel Time on Eastbound I-66: 7am to 10 am

Traffic Volume

Speed (mph)

Travel Time per Mile (min.)

•7:00-8:00 am

•8:00-9:00 am

•9:00-10:00 am

7,000

6,000

6,000

19,000

30.0

25.0

30.0

14,000

14,40

12,000

40,400





Travel Time with No Flow Breakdown(for the same 19,000 vehicles)

Traffic Volume

Speed (mph)

Travel Time per Mile (min.)

•7:00-8:00 am

•8:00-9:00 am

•9:00-10:00 am

8,000

8,000

3,000*

19,000*

55.0

55.0

55.0

8,720

8,720

3,270

20,710*Previous freeway traffic only. Recovered capacity of 5,000 vehicles will attract additional drivers





Annual Benefits of Free Flow on I-66Per Mile

Avg. Trip Length

Total Savings*

•Daily time savings

•Annual savings (total, AM and PM)

•Monetary value**

19,690 10 mi. 196,900 min.

1.64 million hours

$20 million

*Additional benefits anticipated 9 – 10 am due to recovered capacity (5,000 vehicles), including: (1) benefits to 5,000 vehicles; (2) congestion reduction on alternative routes.

**At $12 per hour





The Problem is Solvable• Keeping a small number of vehicles from

arriving at critical times can prevent flow breakdown

• Evidence:▫ Washington DC in August▫ State holiday in California▫ Jewish holiday in Boston

• In each case less than 10% fewer vehicles





Can a Few Vehicles Shift Arrival Time?

• National Household travel Survey:▫ 20% of vehicle trips made during peak travel

periods are made SOLELY to shop▫ Total non-work travel** constitutes:

49% of vehicle trips in AM peak period 75% of vehicle trips in PM peak period

*Source: USDOT, FHWA – National Household Travel Survey 2001

** Includes only trips not made during a commute “tour”





Can a Few Vehicles Shift Arrival Time?

• Options for work trips:1. Shift to transit2. Vanpool or carpool3. Use flextime, or telecommute

• Key is to get a few vehicles off the freeway during the critical period





Can We Prevent Flow Breakdown?

• The three “pull” strategies (transit, ridesharing and flextime/telecommuting) are necessary but not sufficient:

▫ Any reduction in delays due to such shifts will cause “replacement” of reduced traffic by those who had previously been deterred by congestion

▫ Must ensure that user-borne cost of driving stays about the same as before

• Two ways: (1) ramp metering; (2) congestion pricing





(1) Ramp Metering

• Controls merging traffic at freeway entrance ramps, using time delay as a “price” to enter the freeway

• Main issues:

▫ Queues can back up onto arterials and cause congestion

▫ Drivers frustrated by long waits

▫ Those living further out have advantage over those living in central city

▫ Motorists may choose to divert to alternate routes





(2) Congestion Pricing

• Variable toll “price” to manage demand for use of freeway:

▫ Unlike time “price” in ramp metering, user-borne toll cost is not a “wasted” resource – revenue can generate additional benefits

• Main issues:

▫ Motorist perceives that “free” service will be taken away

▫ Some drivers may be made worse off





(3) “Super HOT” Congestion Pricing

• Toll-bypass lane plus modal choices, gives options :

▫ Wait in toll-bypass lane and “pay” with time

▫ Go to transfer area and take fast, discounted transit

▫ Ride toll-free in a certified vanpool or carpool

▫ Pay variable toll and get guaranteed premium service

▫ Pay lower tolls or no toll by traveling earlier or later





“Super HOT” Pricing• Dynamic pricing:

▫ Can manage flow for optimum throughput in real time

▫ Can respond immediately when spare capacity is available by reducing toll rates, benefiting the motorist

• ALL lanes priced:

▫ When only one or two lanes are priced, tolls must be high enough to “price off” a majority of users

▫ When all lanes are priced, only about 10% of users must be priced off at the critical “breakdown” time– so tolls are a lot lower, and 90% are willing to pay them





“Super HOT” Incident Management

• Overhead lane controls at short intervals:

▫ During incident, one “clear” lane restricted for buses and HOVs

▫ Any spare capacity in the restricted lane managed for free-flow using an “additional” variable toll for SOVs willing to pay for premium service

▫ All other vehicles credited with amount of toll paid, if guaranteed speed is not experienced





Toll-Bypass Lanes• With 10-15% of travelers shifted to other modes or

times-of-day, all remaining vehicles could be accommodated, so toll-bypass lanes would have zero delays to begin with

• This would encourage more drivers to use the lane, until the queue is long enough that queue-delay “cost,” as perceived by those with the lowest value of time, would be equal to the toll rate

• Assuming a 5 min. queue delay, and a queue

discharge rate of 15 vehicles per min., the toll-bypass lane would need to accommodate 75 vehicles





“Super HOT” Concept Summary

• Manage traffic flow on all lanes of a freeway

• Variable tolls:▫ At bottleneck locations only▫ During peak periods only

• Complementary strategies▫ Operations – ramp metering, toll collection, lane controls▫ Discounted transit services▫ Certified vanpools and carpools – toll-free▫ Telecommuting and flextime▫ Multi-modal traveler information





Advantages• Reduces congestion now on whole freeway network

• Creates an HOV network and a “fixed guideway” transit network practically overnight

• Advantages relative to priced lane networks:▫ Costs lower – less right-of-way, pavement, easier

freeway-to-freeway connections ▫ Capacity per lane higher▫ Safety – less weaving▫ User cost - lower toll for premium service▫ Entire facility congestion-free





Feasibility of a Super HOT Highway Network

• Toll rates• Costs to implement• Revenues• Social benefits





Prototypical Urban Network

• 100-mile, severely congested freeway network, avg. 6 lanes

• Price all lanes – peak periods only

• New express bus services with heavily discounted transit fares

• Park-and-ride at transit transfer sites

• Toll-bypass lanes at toll gantries at about 5-mile intervals





Average Peak Period Toll Rate for 10-mile Freeway Segment

•Prior peak period avg. speed

•Time saved over 10 miles

•Willingness-to-pay of 50% of travelers (20 cents/min. saved*)

30 mph

10 min.

$2.00*

*Based on average value of time of $12.00, 50% of travelers value their time equal to or higher than $12.00 per hour





Annual Highway Costs for 100-mile Network (million $)

Annualized capitalAnnual O & M costTotal

$ 10 * $ 20$ 30

*Based on total capital cost of $127 million, covering operations technology and toll-bypass lanes





Annual Transit Costs for 100-Mile Network (million $)

Transit fare subsidy

Parking at park-and-ride lots

Total

$49

$8*

$57

*Annualized cost, including annualized capital cost plus annual maintenance costs





Annual Costs for 100-mile Multimodal Network (million $)

Highway

Transit and park-and -ride

TOTAL

$30

$57

$87





Annual Benefits for 100-mile Multimodal Network (million $)

Delay reduction*

Reduction in wasted fuel

TOTAL**

$250

$120

$370

*At $12 per hour

**Freeway only – does not include potential reductions due to reduced arterial congestion





What This Means

• Use of congestion delay to allocate scarce roadway space during rush hours costs $370 million a year

• Using a “Super HOT” pricing system instead would cost only $87 million annually, and would in addition provide other economic and quality of life benefits





Costs vs. Revenues and Benefits (million $)

CostsRevenuesSurplus

BenefitsB/C ratio ($380 M./$122 M.)

$87$200$113

$3704.4





What This Means

• “Super HOT” highway network can be financially self-sufficient

• Benefits will exceed costs by a 4 to1 ratio (conservatively estimated).

• Potential to get public acceptance since no one is actually made worse off – although some could still perceive differently

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