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Stanford Study to Try Cold Cash and Social Game to Relieve Rush Hour Traffic

Stanford graduate student Chinmoy Mandayam adjusts one of the radio-frequency identification scanners installed on campus for the Capri project. Credit: Tom Yue

Cash prizes for getting to campus late or leaving early? Even Stanford University’s hard-working employees and students may be tempted to take part in a new study.

Most drivers with a university parking permit can now enroll in Capri (Congestion and Parking Relief Incentives), a program that seeks to reduce rush-hour traffic in the area. The crux of the study is motivating people more efficiently by offering a chance at a larger reward rather than a sure-fire small one. The research project’s director, Balaji Prabhakar, professor of electrical engineering and of computer science, has used the concept in similar transportation studies in Bangalore and Singapore, as well as in a wellness project in the United States.

“You probably wouldn’t jump out of bed early every day for 10 cents,” said Prabhakar. “But the raffle effect, where a small amount of money seems like a lot, is well established.”

After enrolling, eligible participants receive a unique identification tag that clings to the inside of their windshield. Scanners installed at the 10 main campus entry points detect users who avoid the weekday 8-9 a.m. rush hour by arriving between 7-8 a.m. or 9-10 a.m.

The system automatically awards credits to those drivers for an online game that pays random cash prizes of $2 to $50. In the evening, players get credits for departing 4-5 p.m. or 6-7 p.m.

Along with trying to make the most of the project’s prize money, the idea is to make social responsibility fun and interactive. In the United States alone, traffic jams waste billions of gallons of gasoline annually, resulting in millions of tons of greenhouse gases. Capri participants can receive a lot of extra credits for the game by getting friends to join. This can be particularly effective (hint!) early in the program’s launch.

Users can then see when a friend has won a prize, and the amount they won. Also, the frequency of non-peak commutes determines a user’s status — from mere “member” up to “platinum” — and that boosts the size of potential rewards.

Parking Component

The second phase of the study will reward drivers for parking at less-used lots to alleviate wasted time and energy at chronically full ones. The parking part of the study is set to launch this autumn.

“We couldn’t think about doing this kind of thing in the 20th century,” Prabhakar said. “With today’s technology, it’s feasible to install low-cost sensors on a wireless network and make use of new Internet technology. For example, we have a Facebook Connect function. You get a unique link to post on your wall. Every time someone clicks that and joins, you automatically get the credits.”

Many drivers will not change their behavior for the odd chance of winning $50, and others inevitably will be rewarded for arriving and leaving during the same off-peak hours they have been driving for years. But that is fine with the people running the project, which includes graduate students Deepak Merugu, Chinmoy Mandayam, and Tom Yue. Optimized incentives, gaming, and the social element are set and adjusted to achieve a social benefit at low cost.

Some 12,000 Stanford drivers are eligible for this program. Reducing traffic by a few hundred cars, especially in the evening rush hour, would be a success.

“You have to work on conditions,” said Prabhakar. “What is the right price? How many vehicles do you want to move? Congestion is a 10 percent phenomenon. A certain number of people drive off-peak because peak isn’t pleasant. If we solve the 10 percent problem, they may move into peak. So, now you have a new equilibrium.”

If the new situation does not meet the program’s targets, the researchers and university will look to tweak the program.

Holders of “A” or “C” parking permits are eligible, which excludes students who live on campus. Employees are advised to seek the approval of supervisors before shifting work hours, but even those who can shift work hours only occasionally can pick one weekday as their “boost day” and receive triple credits. Capri pays rewards at the end of each month in paychecks for employees and, for students, by transferring the cash to a checking account.

Users can elect the certain reward of about 10 cents per trip rather than trying their luck for bigger payouts. Players also can choose to have the game played for them automatically if they do not want to spend the time ascending ladders and sliding down chutes.

The success of earlier trials led to $3 million in research funding from the U.S. Department of Transportation and the university for the Stanford version. A Bangalore, India, study sponsored by Stanford’s Precourt Energy Efficiency Center doubled the number of one company’s commuters arriving before 8 a.m.

The broad transportation study in Singapore launched this January, and initial results indicate that participants’ shift to off-peak travel is nearly at the project’s target of 10 percent, Prabhakar said.

“I’m really looking forward to rolling this out and trying to identify how this can benefit our program,” said Brodie Hamilton, director of Stanford’s Parking and Transportation Services, which is helping to administer the project.

Part of a Larger Effort

The past couple of years, the number of evening rush hour departures has approached the limit of about 3,600 that the university agreed to with Santa Clara County, said Hamilton. “We have all kinds of incentives to get people to use alternative transportation, like riding bikes or taking the train, but some people have to drive. This could incentivize people to avoid the peak commute,” he said.

If successful, the Capri program may continue on university funding alone after the federal funding ends, said Hamilton. “That’s what I’m hoping. I think there’s great potential and it’s why we have worked with Balaji from the get-go.”

Students who live on campus are not eligible, and shift workers will not get credit for arriving at, say, 6 a.m. These groups are not part of the rush-hour problem. Also, six entry points to the campus do not have scanners either due to ongoing construction or because they connect to student and faculty housing areas, where few eligible residents enter the academic campus. The program website has a map of the scanners.

Parking permit holders, including the primary holder of a Stanford carpool permit, can join the program at The study will use arrival and departure data only in the aggregate, and individual information will not be shared with anyone.

Prabhakar will discuss the Stanford and Singapore projects at the Precourt Institute for Energy’s weekly Energy Seminar on May 14.

Mark Golden works in communications at the Precourt Energy Efficiency Center at Stanford University.

Media Contacts:

Denise Murphy, Department of Electrical Engineering: (650) 725-1606,
Mark Golden, Precourt Energy Efficiency Center: (650) 724-1629,

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