From the Rural ITS Toolbox report: Subsection 7.1 Speed Warning Systems (Truck Speed Warning System)
A truck speed warning system was deployed on a downgrade curve along I-70 in Glenwood Canyon, Colorado by the Colorado DOT. The curve tightens from 7 to 5 degrees. This stretch of roadway had a history of severe runaway truck accidents. If a truck is detected (via radar) exceeding the posted speed, then the truck's speed is posted on a dynamic message sign. The sign displays, “YOU ARE SPEEDING AT [XX] M.P.H. 45 M.P.H. CURVE AHEAD.” The system has been in operation since September 1996. The cost of the system is estimated in the range of $25,000 to $30,000.
System cost: $25,000 to $30,000 (1996).