8 Work Zone Safety
8.1.2 Speed Monitor Display - Iowa
The information on the Speed Monitor Display System was obtained from the Midwest States Smart Work Zone Deployment Initiative Year One Report.22
Impetus for the Activity
The States of Iowa, Kansas, Missouri and Nebraska formed the Midwest States Smart Work Zone Deployment Initiative to test and evaluate technologies for improving safety and efficiency of traffic operations in work zones. By working together, the agencies avoid unnecessary duplication of research through sharing of research results.
Criteria for System Selection (Hardware and Software)
The group held a series of three workshops to identify work zone problems, to define solutions and to select the technologies for evaluation. Potential solutions were presented by technology providers, and these solutions were matched with work zones on specific construction projects. The Speed Monitor Display System, provided by MPH Industries, Inc., was matched with a work zone in Iowa.
Description of the System
The Speed Monitor Display system was deployed and evaluated during the 1999 construction season on a rural work zone on I-35. Like the SpeedGuard system, it measures vehicle speed and displays it to encourage drivers to slow down. However, unlike the SpeedGuard system, the Speed Monitor Display is pole mounted. It uses a K-band radar unit (which also sets of radar detectors in addition to measuring speed) and a 2-character LED display. The overspeed option causes the display to flash when the measured speed is greater than a set threshold, which was set at 89 km/h for this evaluation. Power was supplied by a solar panel and battery assembly.
System Performance
No problems with system performance were noted in the report.
System Effectiveness Evaluation
The Speed Monitor Display system was formally evaluated. The evaluation team looked at mean speeds, compliance with the speed limit, and the number of vehicles in the 16 km/h pace. Reductions in mean speed following deployment of the system were not significant. However, the proportion of vehicles complying with the speed limit increased, as did the number of vehicles in the 16 km/h pace.
The evaluation team noted that many drivers noticed the display too late for them to read it and respond accordingly. The evaluation team recommended that larger character heights be used for interstate work, after concluding that the 18” character height was not legible enough for interstate work zone applications.