Controlling Vehicle Speeds in Highway Construction Zones

The objective of this project was to evaluate the effectiveness of alternative treatments for controlling vehicle speeds in work zones. Field studies were conducted at three rural, high-speed locations, two urban freeway work zones, and five arterial locations. Three treatments were investigated in the project: a radar beam that would activate motorists’ radar detectors, a special work zones speed limit sign with flashing beacons, and a speed trailer that monitors vehicle speeds and displays this information to the driver. Vehicle speeds were collected in work zones in a before period, with the normal traffic control plan in operation, and in a during period, with the supplemental treatment in place. The study found that the radar was ineffective in reducing vehicle speeds through construction zones, perhaps because those motorists with radar detectors could see that speed regulations weren’t being enforced. The work zone speed limit sign with beacons was also ineffective. In applications on urban arterials, the speed trailer was effective in reducing speeds by 4 to 5 mph; use of this treatment on an urban freeway in conjunction with enforcement also resulted in improved speed compliance. The study recommends that work zone speed limits be set realistically, that the speed trailer be used more extensively, and that other, non-engineering solutions be explored.