The travel times shown on the DMS are provided to give motorists an idea of the congestion on the route(s) ahead of them so that they can make route decisions or be ready to react to slower traffic. MDOT contracts with a traffic data provider that uses a variety of sources (such as cell phone signals, GPS on fleet vehicles, and MDOT’s roadway speed detectors) to build a model of traffic-flow speed for segments on the roadways. This data provides the average speed of vehicles that have traveled the segment in the most recent time period. This average speed is used by the MDOT Advanced Traffic Management System software to calculate the time it would take a vehicle to travel the distance from the DMS to the destination shown on the sign. The system sends an updated calculated travel time to the DMS every two minutes.
MDOT’s DMS usually display one or two destinations and includes a distance to the destination to help motorists determine if the speed is slower than expected. On some DMS, travel times for two alternate routes to the same destination are shown.
When travel times are higher than the normal “free-flow speed,” then motorists know that something is going on. When there is an impact on the roadway, such as a lane closure due to a crash or a planned event, the TOC will either override the travel time message or add the information on a second phase. Watch this video to learn about travel times and real-time information.