Work Zone Speed Reduction Utilizing Dynamic Speed Signs

A simulator study was used in this research to determine speed compliance based upon dynamic
speed design and presence. The scenarios designed for this research simulated driving through a
highway work zone with a right lane closure. Each participant drove through a control scenario
and four experimental scenarios subdivided into five areas for data collection. The four
experimental scenarios included dynamic speed signs in place of the regulatory speed limit sign
as follows: (1) Steady ‘SLOW DOWN 45’, (2) Flashing ‘SLOW DOWN 45’, (3) Steady
‘SPEED LIMIT 45’ and (4) Steady ‘SPEED LIMIT 65’. The five areas included the following:
(1) Before the first work zone sign, (2) Between the first work zone sign and the dynamic speed
sign, (3) Between the dynamic speed sign and the lane closure, (4) Between the lane closure and
the end of the work zone, and (5) After the work zone.
Comparisons were made of the measures of effectiveness (speed, lane position,
acceleration, deceleration, gap, time to collision, latency of visual detection, average fixation
durations and the proportion of target fixations) to assess compliance with the speed limit and
changes in driver behavior. When using dynamic message signs stating ‘SLOW DOWN 45’,
participants maintained the speed limit prior to entering the work zone and through the work
zone as compared to scenarios using regulatory signs or dynamic message signs displaying the
speed limit. The dynamic message signs did not create unsafe driving conditions based upon the
analysis of the other measures of effectiveness studied.