A project to bring variable speed limits to one of Utah’s busiest canyon highways has been implemented by the Utah Department of Transportation.

February 20, 2014

PROVO, UT—A project to bring variable speed limits to one of Utah’s busiest canyon highways has been implemented by the Utah Department of Transportation. The system uses data from SmartSensor HD to determine the safest speeds for existing conditions, and new speeds are posted in real time on variable signs. If successful, the program may lead to other deployments throughout the state.

The Parley’s Canyon stretch of Interstate 80 just east of Salt Lake City is heavily travelled and often becomes treacherous, especially during winter storms. Variable speed limits are meant to give drivers a better idea of what are reasonable speeds during certain conditions, with the goal of improving traffic flow in the canyon by allowing drivers to make “better informed” decisions.

“Instead of guessing, we can give drivers feedback about speed limits in storm events and minimize the likelihood of speeding,” says Chris Siavrakas, P.E., PTOE and project manager for UDOT.

The system utilizes a number of different technologies to monitor real-time conditions: SmartSensor HD monitors traffic; environmental sensors measure the slickness of the road along with temperature and humidity; and traffic cameras indicate visibility. Traffic engineers will analyze the data and determine the speed at which vehicles will most safely traverse the canyon; those speeds will be posted to variable speed limit signs installed along the highway and will immediately become enforceable.

An initial deployment of eight eastbound signs and seven westbound signs was installed in January 2014. Parley’s Canyon was selected as the pilot site because of the impact weather has on that stretch of road, and because much of the infrastructure necessary for the project, including reliable power supplies and previously installed sensors, was already in place. Other locations in Utah have already been identified for variable speed limits should this pilot prove successful.

“We are receiving positive feedback from the public,” says Siavrakas. “Some are saying a system like this is long overdue.”

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Photo courtesy of Utah Department of Transportation