Effectiveness of countermeasures to reduce vehicle speeds in freeway work zones

Slowing motorists within work zones on high-speed roadways continues to be a challenge for highway authorities in all jurisdictions. Many work area traffic control manuals (WATCM) limit the speed reduction on high speed facilities to not be more than 20 km/h on the premise that a larger reduction is not practically achievable. The result is that workers on high-speed facilities are often exposed to excessive vehicle speeds in live lanes adjacent to their work sites. This study identified and evaluated supplemental traffic control countermeasures that will achieve speed reductions beyond 20 km/h. The countermeasures tested included singularly and combinations of: floating speed zones (FSZ); traffic control person (TCP); narrow lanes; radar speed display board (RSDB); variable message sign (VMS); and a fake police vehicle. The top ranked countermeasures, TCP and FSZ, fake police vehicle and FSZ, and the RSDB and FSZ, resulted in mean speed reductions of 23 km/h, 19 km/h, and 19 km/h, respectively, and typically with significant reductions in speed dispersion.