A new report by the Michigan Department of Transportation (MDOT) examines the effectiveness of speed warning technologies across critical speed-change contexts in order to provide guidance to support future installation and operation of such treatments.

Speed-related crashes remain a critical concern across the United States. A substantial proportion of these crashes occur in contexts where drivers are required to quickly adjust their speed to navigate changing roadway geometry or land-use. These critical speed-change areas include freeway exit ramps, horizontal curves, highway transitions into rural communities, and freeway to non-freeway transitions.

While traditional warning treatments, including signs, delineation, and beacons have been used for decades, MDOT recently expanded the implementation of advanced signing technologies to better warn motorists approaching speed change areas. Such strategies have the potential to reduce excessive speeds and resulting crashes in speed-change areas. However, for many types of critical speed-change scenarios, little research has been performed on the speed reduction effects of such strategies, and those studies that have been performed have typically only considered daylight and favorable weather conditions.

The speed warning technologies evaluated in this research included dynamic speed feedback signs, flashing LED chevron systems, weather-activated slippery curve warning systems, and targeted winter weather messages on changeable message signs.

Read the full report