About the research
A radar actuated speed display board was deployed in a rural Interstate work zone in which traffic was reduced to one lane in each direction. Speeds were measured at several locations over a span of about a mile. Data were collected without the display for one week and then with the display in operation for another week. Comparison of traffic characteristics showed statistically significant decreases in mean speed, 85th percentile speed, and percent speeding, both at the display location and as much as half a mile downstream. The mean speed reduction between the before (without the display) and after (with the display) data was about 3 mph at the display and about 1 mph half a mile downstream. Data were also collected for several hours while a Kansas Highway Patrol (KHP) vehicle was positioned at the same location. Changes in speed characteristics relative to baseline conditions were similar to those observed with the speed display at the display/vehicle location. A half-mile downstream, though, speeds were well above baseline speeds when the KHP was present.
Vendor: Speed Measurement Labs