Effects of Speed Feedback Trailer Positioning and Presence of Law Enforcement on Driver Behavior in Freeway Work Zone Lane Closures

Abstract

Work zone speed limits and management of work zone speeds continue to be critical areas of concern for transportation agencies. This field study sought to evaluate select strategies for improving compliance with work zone speed limits, which included a speed feedback trailer (SFT) and the presence of law enforcement.  A SFT was tested at the start and end of the taper within a freeway work zone single-lane closure to determine which position provided the most favorable speed reduction effects.  In general, the magnitude of the speed reduction effects was the 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.  When SFT was positioned near end of the taper, the average speed was 1.5 mph and 0.8 mph lower at the SFT location and at the end of the measurement area (2,150-ft beyond the start of the taper) compared to no SFT conditions. The second 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 at this location reduced work zone speed by approximately 5 mph, which increased to 7 mph shortly beyond the end of the work zone as motorists passed by the police cars positioned on the shoulder.  These speed reduction effects were only observed when at least one law enforcement vehicle was visibly present at the site.