The next phase of variable speed limit signs on Interstate 80 have been turned on and will be officially operating February 1st.

Variable  speed limits were introduced  in 2009 between Laramie and Rawlins with the goal of limiting accidents and reducing road closures.

Theresa Herbin, for  the Wyoming Department of Transportation, district three, says the first phase proved very successful.

"They found an amazing reduction in the number of crashes and the closures."

This year Wydot extends the signs from just east of Rocksprings to Greenriver, with a contract out to put more in place on the far western side of the state near Evanston.  Herbin explains that the system works by using sensors that detect when traffic is slowing.

"They're pretty crafty little devices. There are  road sensors that the Transportation Management Center in Cheyenne can use to actually monitor the average  speed the traffic is slowing."

She says a combination of sensors, web-cams and real time observations combine to inform the TMC when to enact the variable speed limit reducing speeds at intervals of five miles per hour.  The new signs between Rocksprings and Greenriver come with a price tag of just over $900,000.  The signs go live on February 1st.