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On the Road...Again: Transportation engineer's plan could relieve roadway crowding by encouraging trips at off-peak times

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Motorists have to pay a fee at certain times of day to drive in parts of London, Stockholm and Singapore.

Those cities have adopted a concept called congestion pricing, in which motorists pay to enter crowded parts of the cities at busy times of day. Those who don’t want to pay find alternate, perhaps cheaper forms of transportation.

Kara Kockelman
Engineering Professor Kara Kockelman devised a concept called congestion-based credit pricing to encourage motorists to hit the road when others aren’t.

The cities’ programs vary by degree. In London, it’s a flat rate and once inside the restricted area one can drive around all day. In Stockholm, the fees vary by time of day. In Singapore, the downtown restrictions are complemented by variable tolls on the surrounding freeway network.

The result in each city is less densely packed streets, better traffic flow and less pollution.

These are examples of how metropolitan areas are trying to cope with the increasing problem of congestion by regulating access to scarce road space.

Motorists spend increasing amounts of time and fuel sitting in dense traffic. Traffic congestion is a top problem in urban areas throughout the United States and the world. Traffic congestion costs the U.S. economy $100 billion a year in delays, wasted fuel and other losses.

Kara Kockelman studies traffic solutions as an associate professor in the Department of Civil, Architectural and Environmental Engineering in the Cockrell School of Engineering at The University of Texas at Austin.

She wants to make pricing policies even better with an idea called credit-based congestion pricing. Drivers receive credits they can spend to drive on crowded roads during peak times. Or they can spend the credits more judiciously by traveling at off-peak hours.

“It’s everybody having a piece of the road system,” she said. “How you want to use it is up to you.”

Under credit-based congestion pricing, everyone would get a piece of the network in the form of a monthly credit.

It's everybody having a piece of the road system. How you want to use it is up to you. Dr. Kara KockelmanThose who drive at non-peak hours or take alternative transportation can end up even or with extra credit. Those who must travel at high-traffic times—and do so often—would use their credits and then pay into their toll tag accounts. There also could be a system in which people trade credits.

The idea, Kockelman said, is to give people financial incentives to stay off the roads at peak times or to take public transportation or carpool.

Of course, congestion isn’t the only reason to charge roadway users, said Kockelman, a William J. Murray Jr. Fellow in Engineering at the university.

“The infrastructure itself is rather costly to provide—and then maintain,” she said. “And communities may want to impose different prices on different types of vehicles. Not because they damage the pavement, but because they emit different levels of noxious pollutants and greenhouse gases, and consume more space.”

Kockelman said credit-based congestion pricing is more equitable for low-income drivers than conventional congestion pricing. “They may end up with extra credits at the end of each month, cash these out, effectively, and buy things they value more, including bus passes, food and health care,” she said. Especially hard-hit populations could apply for additional credits.

Implementing credit-based congestion pricing won’t be a Sunday drive. Every vehicle would have to be equipped with a transponder in order to be detected by roadside readers.

But much of the technology is being used today. It’s what allows motorists to drive on toll roads without slowing down or stopping to pay tolls.

Kockelman and a former student used data collected by the North Central Texas Council of Governments and computer modeling to see what might happen if credit-based congestion pricing was used in the Dallas-Fort Worth area.

Stuck in Traffic: Annual Hours of Delay by Urban Areas: No matter where you live in the United States, there's a good chance you're spending more time in traffic. The hours of delay the average driver experiences has increased pretty much across the board in the decade between 1995-2005.The study showed it would reduce overall vehicle travel by 7 percent, but raise speeds by 20 percent. That means people could get to their destinations faster. So even most of those who end up paying out of pocket can perceive a net benefit.

The researchers estimate the start-up cost of the system—transponders, cameras, computers and administration—for the Dallas-Fort Worth area would be $53 million, or $11 per resident. Recurring costs would be $260 million a year, or $54 per resident.

Dallas-Fort Worth area residents are already paying $560 a year as the cost of congestion, according to Texas Transportation Institute’s annual Urban Mobility Report.

Getting people to buy into congestion-based credit pricing will take time, Kockelman said. There is a lot of education of government officials and residents to do.

In a survey conducted across Texas a few years ago, 56 percent of the respondents were in favor of converting existing roads to tolled roads if credit-based pricing were used.

Kockelman has briefed Texas legislators about the concept and has delivered talks to transportation groups about it.

There is at least one group that likes the idea.

The American Society of Civil Engineers has awarded Kockelman the 2007 Harland Bartholomew Award. It cites "her many planning contributions, including her novel credit-based congestion pricing theory, which has the potential to revolutionize roadway operations by eliminating recurring traffic congestion and allocating scarce roadway space in a equitable fashion."

Kockelman is one of several engineering professors at the university who work on solving traffic problems. She is part of one of the top programs in the country, a program that rivals those at the University of California, Berkeley and the Massachusetts Institute of Technology.

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  Updated 18 December 2007
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