About the research
This study sought to identify best practices for setting work zone speed limits by state departments of transportation (DOTs) and to evaluate select strategies for improving compliance with work zone speed limits. This was achieved by synthesizing information from a literature review, a state DOT survey, and field evaluations of select speed management strategies.
The state DOT survey found that work zone speed limits are typically established based on the characteristics and conditions of the site, including permanent speed limit, facility type, worker presence, positive protection, work duration, and type and location of work activity.
Work zone speed limit reductions of 10 mph are most frequently utilized on high-speed facility types, with further reductions provided based on worker presence in the absence of positive protection. While the 10 mph speed limit reduction is often viewed as effective, the use of a 45 mph work zone speed limit when workers are present may require the use of additional speed reduction countermeasures to be effective.
Research studies have generally shown several types of work zone speed management strategies, such as speed display signs, law enforcement, variable (dynamic) speed limits, temporary rumble strips, and portable changeable message sign (PCMS) messages, to be effective in reducing vehicle speeds in work zones.
The work zone speed management strategies most frequently implemented by state DOTs include higher fines for speeding in work zones and lights on contractor or maintenance vehicles. While DOTs generally view law enforcement with an officer present as the most effective strategy for managing work zone speeds, they also perceive the availability of law enforcement as the greatest challenge to managing work zone speeds, followed by driver indifference and distracted drivers.
Based on the findings from the literature review and DOT survey, a field study was performed to assess the effectiveness of two work zone speed management strategies, which included a speed feedback trailer (SFT) and law enforcement. In general, the magnitude of the speed reduction effects were greatest in the general proximity of the SFT. Accordingly, positioning the SFT near the end of the taper led to lower speeds for a more sustained distance into the work zone compared to when the SFT was positioned near the start of the taper.
A second field evaluation assessed the effectiveness of a specialized work zone enforcement strategy that included a covert speed measurement vehicle positioned near the end of the work zone along with four police cars positioned just beyond the end of the work zone to stop speeding drivers. The visible presence of law enforcement activities at this location reduced work zone speeds by approximately 5 to 7 mph.