In a few places around the world–such as downtown London–drivers pay higher tolls for entering city centers at peak rush hour. The idea of “congestion pricing” is to reduce traffic and pollution by giving drivers an incentive to travel at off-peak times.
Now a professor at the University of Texas at Austin has shown how a complex extension of this idea could greatly speed up rush-hour traffic flow throughout an entire network of highways and secondary roads in a U.S. metropolitan region. Using a computer model of driver behavior on the freeway system around the cities of Dallas and Fort Worth in Texas, University of Texas civil engineer Kara Kockelman showed that imposing highway tolls wirelessly–and increasing those tolls sharply on heavily traveled roads during peak times–would induce enough people to change their plans to increase average travel speeds by 25 miles per hour during rush hours on many key stretches of highway. The computer model takes into account everything from the frequency of trips to the value that drivers place on saving time.
Under the scheme, cars would be monitored with radio-frequency identification (RFID) or global positioning system (GPS) technologies that would track where and when they are driven. Drivers would pay mileage-based and location-based tolls on a sliding scale: up to 20 cents per mile for driving through bottleneck stretches at the busiest times.
Kockelman says such simple market mechanisms can solve traffic problems without requiring the construction of new roadways. “Meeting travel needs is largely a function of sending appropriate pricing signals to travelers,” she says. “We can allow them to make their own decisions, rather than having to expand capacity in our nation’s already extensive roadway networks.”
And it doesn’t have to cost drivers much or hit low-income drivers hard. That’s because drivers would get a fixed monthly toll “credit” and pay out of pocket only when they exceed the monthly allotment. She calls it “credit-based congestion pricing.” The idea is that those who must use the highways frequently at peak times will pay the most, while others will pay little or nothing. The model results suggest that most of the region’s population would benefit, because the value of their saved time would exceed the toll costs, she says.
The work is early-stage research. To be sure, wide adoption would require drivers to accept having their travel habits electronically tracked. But similar concerns accompanied the installation of RFID tags at today’s tollbooths. Millions of drivers soon forgot about privacy worries when they began speeding past the coin-tossers at tollbooths. And privacy concerns could be addressed if third-party companies handled account information.
If Kockelman’s model is right, the expanded adoption of such technology could provide substantial traffic relief for millions of drivers around U.S. metropolitan areas. “I think most residents of congested regions will feel it’s worth a shot,” Kockelman says. “Congestion is the number-one concern cited by residents of most urban regions in the U.S.”
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