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How ATM symbols work

 Lane closed         Lane open         Current speed limit

 Merge left           Merge right         Merge left or right

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.


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.

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

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.