Getting Out Of The Heat: Traffic Congestion "Temperature" Could Forecast Problems And Help Drivers Avoid Lengthy Delay

People plan their days according to the weather forecast, but they can't do that with traffic -- at least not quite yet, said Dr. John Leonard, an associate professor in the School of Civil and Environmental Engineering.

Leonard is developing a cutting-edge traffic flow model that analyzes a variety of historical data and a host of variables to predict the next day's traffic conditions. He calls it a traffic congestion "temperature." The model will also estimate current travel times from point to point.

"People need a simple-to-understand number -- even if it doesn't have a physical meaning -- to represent traffic congestion," Leonard said. "We need to publicize it daily so people start to develop a personal understanding of congestion and plan accordingly."

Leonard is creating his model using the past two years' data from traffic surveillance systems -- such as the Georgia Department of Transportation's 300-plus video cameras installed on freeways in metro Atlanta. The model also incorporates data from commonly used loop detectors on roadways.

One byproduct of Leonard's research is a graphic representation of congestion. For each day of data, he is creating "star" diagrams that graphically show travel time estimates from various points of origin to any of the five points on the "star" created from a map of the city's major highways. Then he will examine the data for trends and try to correlate them with variables such as special events, hotel occupancy, time of day, holidays, schools in session, weather and, of course, vehicle accidents. An analysis of this information, combined with current traffic conditions, would then yield a prediction of traffic congestion for the next 24 hours.

In Atlanta, the points of origin would be major workplaces or centers of activity, such as Tech, Coca-Cola, the airport and malls. The travel time estimates on Atlanta's "star" diagram would go to: Interstate 285 at I-75 north; I-285 at I-85 north; I- 285 at I-75 south of the city; I-285 at I-85 south of the city; and the airport.

Leonard believes if people became familiar with a traffic "temperature," they would change their travel behavior and ultimately lessen traffic congestion.

"Many people have the flexibility to plan their trips according to traffic congestion," Leonard said. "With this sort of pre-trip information, people could decide whether to leave now or wait 10 minutes. . . . This could spread the peaks out a little and improve travel times for everybody."

Leonard sees a particular benefit for people who make a lot of discretionary trips and a benefit to couriers who might be able to reschedule or reroute deliveries.

Publicizing the traffic congestion index will be key to its having the intended effect. Leonard envisions freeway message board, radio, television and Web site distribution. In fact, he has an early prototype for Atlanta available online at: http://traffic.ce.gatech.edu/trafficweather.

"We're not ready for prime time yet," Leonard said. "We have to work on getting the prediction close. I want to be accurate 90 to 100 percent of the time."

Besides the obvious short-term benefits of a traffic congestion index, long-term benefits would include better traffic planning for the future. This information should also be integrated with ozone pollution forecasting, work that is also ongoing at Georgia Tech, he added.

Leonard's research is now funded internally at Georgia Tech. He has discussed the work with officials at the Georgia DOT, and they are providing historical data. He also hopes to capture the interest of the newly created Georgia Regional Transportation Authority (GRTA). Leonard believes the traffic "temperature" model would fit GRTA's plans for congestion indicators.

Full implementation of the traffic congestion index is probably several years away, Leonard said. Though Atlanta will be the testbed for the index system, it could be implemented anywhere.