Evaluation of Supplementary Traffic Control Measures for Freeway Work-zone Approaches

Controlling traffic in work-zones to improve safety continues to be a major concern for highway agencies. Three traffic control devices: white lane drop arrows, the CB wizard alert system, and orange rumble strips were tested for their effectiveness in improving merging, and reducing speed and speed variance at an interstate highway work-zone in Missouri. Based on the results of the study described, the lane drop arrows, CB message, and rumble strips can be expected to promote some increases in early merging and some decreases in mean speeds of vehicles approaching an interstate highway work-zone with a lane drop. Effects of all three devices on speed variance are inconclusive. However, because of the difficulty in summarizing across the many variables involved (day/night/dawn/dusk, open/closed lane, vehicles class, etc.), it is recommended that anyone considering the use of the devices examine the full report.