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

An evaluation of the effectiveness of speed displays and portable rumble strips at reducing speeds in rural-maintenance work zones is described. Speed displays are radar-activated signs that dynamically display approaching vehicle speeds. The devices were tested on two-lane low-volume, high-speed rural roads where maintenance activities were completed in a single day. 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 test treatment was 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 mean speed reductions approaching the temporary traffic-control zone of up to 11.6 km/h (7.2 mph) lower 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 used. The speed display was generally more effective than the rumble strips at reducing speeds in the advance warning area. Mean speeds were often reduced approaching the activity area, 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.