Driver Response to a Dynamic Speed Feedback Sign at Speed Transition Zones Along High-Speed Rural Highways

Abstract

Research was conducted to assess the effectiveness of a dynamic speed feedback sign (DSFS) as
a speed reduction strategy at speed transition zones along five high-speed rural highways in
northern Michigan. The DSFS was positioned on the shoulder in advance of the reduced speed
limit at each community and was programmed to display speeds of approaching vehicles
alternating with the upcoming reduced speed limit. Using handheld LIDAR guns, vehicle speeds
were tracked through each speed transition area before and after installation of the DSFS. The
DSFS was found to have a significant speed reduction effect throughout each of the five speed
transition zones. The speed reductions generally began when the DSFS came into the motorists’
view, and the speed reduction effect increased as motorists approached DSFS. The greatest speed
reduction effects were observed at the DSFS location itself, where speeds were 3.2 to 7.8 mph
lower with the DSFS present, and these reductions were sustained upon entry to the community.
Similarly, drivers were 78.8 to 92.4 percent less likely to exceed the reduced speed limit with the
DSFS present. Positioning the DSFS further upstream typically resulted in earlier speed
reductions, although this effect become negligible once vehicles reached the reduced speed zone
entering the community. Based on the study findings, continued use of DSFS for speed
management at speed transition zones entering communities on high speed rural roadways is
recommended. When used in this context, the DSFS should be positioned 250 to 650 ft upstream
of the reduced speed limit.