Evaluating Driver Response to a Speed Feedback Trailer at Median Crossovers Within Freeway Construction Work Zones

Abstract

A series of field evaluations were performed to assess the speed reduction effects of a speed feedback trailer (SFT) positioned at various locations before and after a median crossover section within a freeway construction work zone. The SFT was evaluated at three positions at the lane closure taper approaching the median crossover: 1) taper start, 2) taper end, and 3) 800 ft beyond the taper end near the initial R2-1a “Where Workers Present 45” speed limit sign. The SFT was also evaluated within the barrier-divided two-way traffic section after the traffic had crossed over the median. Vehicle speeds approaching the SFT were measured at several locations using LiDAR guns. Positioning the SFT slightly beyond the end of a lane closure taper, adjacent to the nearest R2-1a sign resulted in speed reductions that were both greater in magnitude and sustained further into the work zone compared with when the SFT was located at the taper start or taper end. With the SFT in this position, speeds near the start of the median crossover, which was more than half a mile beyond the SFT and nearly a mile beyond the start of the taper, were 1.4 mph lower compared with when no SFT was present. The SFT was similarly effective for reducing speeds of passenger cars when positioned within the crossover section, although heavy truck speeds were unaffected.