In Colorado, a downhill truck speed warning system installed on a curved section of I-70 reduced 85th percentile truck speeds by 27 percent.
One such best practice is speed warning systems, a tool available for crash prevention and safety. Speed warning systems are effective for locations that experience sizeable speed differentials such as mountain passes or curves that require commercial vehicles to slow more than passenger vehicles. Typical speed warning systems are composed of speed measurement technology, an automatic speed classification system, a weigh-in-motion system, and a dynamic message sign to communicate with drivers. The primary use for this technology is for commercial vehicle operations.
In Glenwood Canyon, Colorado a truck speed warning system was installed in September 1996 to improve safety and reduce runaway truck accidents on a steep section of I-70. The automated system used a radar gun to determine the speed of trucks approaching the curve, and if a speeding truck was detected a dynamic message sign was activated that read "YOU ARE SPEEDING AT [XX] MPH / 45 MPH CURVE AHEAD." The curve, was located on a down grade and curve geometry tightened from 7 to 5 degrees midway. Based on limited sight distance, the maximum design speed for the curve was estimated at 45 mi/h.
Speed studies conducted before and after the system was activated indicated that the warning system reduced 85th percentile truck speeds from 66 to 48 mi/h, a 27 percent reduction.
Author: Deeter, D., H. M. Zarean, and D. Register
Published By: U.S. DOT Federal Highway Administration
Source Date: November 2001
EDL Number: 13477
Other Reference Number: FHWA-OP-01-030URL: http://ntl.bts.gov/lib/jpodocs/repts_te/13477.html
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