Whitemud Drive, Edmonton.
Partnering with the City of Edmonton, the Centre for Smart Transportation (CST) tested a system of digital signs that displayed advisory speeds to drivers along Whitemud Drive, between 111 Street and 159 Street.
“When drivers followed the advisory speed, congestion at on-ramps reduced considerably,” said Wai Cheung, Transportation Services’ technical specialist in advanced traffic analysis. “There was more room between vehicles on the freeway for merging vehicles to slide safely into the flow of traffic.”
On-ramp congestion can cause drivers to brake quickly, creating a "wave" of braking that moves upstream on the freeway. Congestion often remains long after the initial event that causes it.
“The net effect of giving drivers what we call advisory driving speeds was that average speeds during peak periods actually increased by up to 30 km/h,” says Dr. Tony Qiu, Associate Professor and Director of the University of Alberta’s Centre for Smart Transportation.
Advisory driving speeds shortened the duration of overall peak congestion from an hour to only 40 minutes. Travel time between 122 Street and 159 Street was also reduced during peak flow periods by 10 percent or more. To calculate the Advisory Driving Speed (ADS), volume and speed data were collected in real time by sensors embedded in the road and then processed using a complex algorithm. The software developed by the CST processed the data and provided recommendations to the City’s Traffic Operations Centre, which then wirelessly sent updated advisory speeds to dynamic roadside message signs for drivers.
During the pilot, there was also a significant drop in the number of vehicle collisions. There were two collisions, rather than the usual five or six during the same period over the previous three years.
Whitemud Drive was chosen for the test because it experiences a high volume of traffic as well as recurrent congestion during rush hour, which can result in constant stop-and-go movement or even bring traffic to a standstill. Not only is flow an issue, but safety is also a concern. When vehicles must come to a sudden stop, rear-end collisions are more likely to occur. Improving the flow of traffic will also result in increased safety.
Similar technology has reduced collisions and congestion in France, Sweden and the United States.