During regular sunny days, he said, the speed limit will remain at 65 mph.
But during bad weather, a traffic engineer will look at data from road sensors that show how slick the road is, along with the canyon's temperature and humidity. Other data will show how fast traffic is moving, and cameras can show how good visibility is.
After taking all those factors into consideration, the traffic engineer will remotely alter the speed limit signs – and send alerts to the Utah Highway Patrol. "It becomes the enforceable speed limit," Miles said.
The system will operate on I-80 from the mouth of Parleys Canyon to near the Jeremy Ranch exit. Eight electronic signs are in eastbound lanes, and seven in westbound lanes.
"This is the first such system in Utah. There are others operating in Nevada and Colorado. Wyoming and Washington have them on the Interstate system in areas much like Parleys," Miles said.
UDOT chose to build the state's first system in Parleys because of sometime treacherous weather there, Miles said, plus, "there is a lot of traffic, and we have the infrastructure to support it" including connections to computer networks, road sensors and electricity for the signs.
UDOT has been testing software and hardware for the system for several months.
If it works well "we'll take a look at this at other locations, maybe Sardine Canyon [near Logan] or Provo Canyon," and other sites have also been discussed, Miles said. "This is a good tool to affect safety."