In England, a variable speed limit system on the M25 freeway increases average travel times, but promotes proper following distances between vehicles and creates smoother traffic flow.

14 March 1997
M25 freeway; England

Summary Information

Speed limits were adjusted in response to the level of congestion on the M25, one of the most congested freeways in England. Using dynamic message signs (DMS) and loop detectors measuring traffic density and speed, speed limits were lowered in increments as congestion increased. Speed cameras were used to enforce the speed limits, resulting in 26,000 fines.

The study found that motorists were more inclined to keep to their lane when a "faster lane" no longer existed. They were also more inclined to keep to the inside lane and to keep proper distances between successive vehicles, resulting in smoother traffic flow which actually increased average travel times of traffic. Results show that traffic accidents decreased by 28 percent during the 18 months of operation.

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Variable Speed Limits Reduce Accidents Significantly in the U.K.

Author: Borrough, Peter

Published By: The Urban Transportation Monitor

Source Date: 14 March 1997


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photo enforcement, speed cameras, automated speed enforcement, automated enforcement, photo radar

Benefit ID: 2000-00001