Active Traffic and Demand Management - How ATDM symbols work

Photo showing Active Traffic and Demand Management symbols in use


Lane closed symbol Lane closed      Lane open symbol Lane open      Current speed limit symbol Current speed limit



Merge left symbol Merge left      Merge right symbol Merge right      Merge left or right symbol Merge left or right



Overhead signs are blank and the normal 60 mph speed limit is displayed

When traffic is flowing normally, the overhead signs are blank and the normal 60 mph speed limit is displayed in either side of the sign bridge.


overhead signs automatically reduce the speed limit

When traffic up the highway begins to slow down, overhead signs automatically reduce the speed limit to prepare drivers for slower traffic ahead, reducing sudden braking and collisions. Message signs offer instant traffic information, such as congestion or blocking incidents as they happen miles up the road.


speed-limit displays switch intermittently to directional arrows

The overhead speed-limit displays switch intermittently to directional arrows, and a traffic information sign warns of a lane closure ahead.


red X's indicate which lanes are closed

At the point of a blocking incident, such as a collision or a stall, red X's indicate which lanes are closed. Meanwhile, the speed limit automatically increases as traffic returns to normal.