Evaluation of Speed Displays and Rumble Strips at Rural Maintenance Work Zones

This paper describes an evaluation of the effectiveness of speed displays and portable rumble strips at reducing speeds in rural maintenance work zones. Speed displays are radaractivated signs that dynamically display oncoming vehicle speeds in large numerals. The devices were tested on low-volume, high-speed rural roads where maintenance activities were completed in a single day. All work zone sites were two-lane facilities with 3 m (10 ft) shoulders. Speed and volume data were collected for cars and trucks as they traveled through four work zones. These data were collected when no work zone traffic control was present, when normal work zone traffic control was set up, and when the speed display or portable rumble strips were installed.

The results for the portable rumble strips were mixed, with passenger cars experiencing less than a 3.2 km/h (2 mph) reduction in mean speed approaching the temporary traffic control zone. The impact of the rumble strips on trucks was more pronounced, with significant mean speed reductions approaching the temporary traffic control zone of up to 11.6 km/h (7.2 mph) less than normal traffic control. The percent of vehicles exceeding the speed limit in the advance warning area was also reduced when the rumble strips were in place.

The speed display was generally more effective than the rumble strips at reducing vehicle speeds in the advance warning area. Mean speeds were often significantly reduced as both cars and trucks approached the work zone, with speed reductions of up to 16.1 km/h (10 mph) being achieved. The percentage of vehicles exceeding the speed limit was also reduced in the advance warning area from when only normal work zone traffic control was used.