A small-scale study of truck drivers who experienced a dynamic truck down hill speed warning system in Colorado indicated that most drivers thought it was helpful.
The system used weigh-in-motion sensors, inductive loop detectors, and computer hardware and software to monitor vehicle speed, weight, and axle configuration for trucks. A computer algorithm was used to compute a safe descent speed for each type of vehicle weighing more than 40,000 pounds, and a recommended speed/warning message was posted on a dynamic message sign (DMS) at the end of the tunnel.
To evaluate system impacts, truck weight, speed, and axle configuration data were collected upstream and downstream of the posted downhill warning message. At the Dumont weigh station located upstream of the tunnel, video camera and weigh station data were collected to supplement the weight and speed data collected by the WIM system inside the tunnel and at a video camera located at the tunnel exit. Two miles downstream, another video camera system was installed.
Truck activity was monitored with the system "on" and the system "off." The system was "on" from 11 AM to 1 PM on May 19 and May 21, 1999, and the system "off" from 11AM to 1PM on June 2 and June 4, 1999. Weather conditions were similar on each day and speed data upstream and downstream of the dynamic message sign was able to be calculated for approximately 30-40 trucks during each 2-hour sampling period. A two-tailed t-test was used to compare average truck speeds with and without the system active and an analysis of covariance model was used to account for an increased number of lighter (i.e. faster) trucks observed when the system was "off."
During the days when truck activity was monitored, truck drivers that visited the Dumont weigh station office were asked a series of six easy questions related to their awareness and opinion of the downhill speed warning system. Of the 40 drivers surveyed, 22 read the sign, and 21 of 22 indicated the warning sign would help truckers travel at a safer descent speed.
Author: Janson, Bruce N.
Published By: Colorado DOT
Prepared by the University of Colorado for the Colorado DOT
Source Date: 15 December 1999
EDL Number: 11963URL: http://ntl.bts.gov/lib/jpodocs/repts_te/11963.pdf
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