Motorway slip road traffic light scheme completed
28 April 2009
A national expansion of traffic lights on motorway slip roads has now been completed and is expected to help ease congestion ahead of motorway junctions.
The Highways Agency has now fitted and activated 85 motorway junctions with slip road traffic lights.
The traffic lights system, known as 'ramp metering', is designed to smooth motorway traffic flow, rather than increase average speeds, by cutting the bunching effect which happens on motorways just before junctions.
Automatically operated, with the possibility of an override by a traffic control centre, the lights come into action when traffic is at its busiest, usually when the motorway speed falls below 50mph. The lights hold traffic on the slip road for a short period of time (typically 20 seconds) before releasing vehicles onto the motorway.
Sensors in the slip road will turn the lights green if traffic queues back up causing congestion on roundabouts or local roads.
The expansion completes a roll-out programme initiated in 2007. However, the first ramp metering system in the UK was on the M6 at junction 10 and was set up in 1986.
While the current expansion plan is now completed, the Highways Agency has said it will look at fitting ramp metering at a few more junctions following an increasing in funding through the Government's financial stimulus package.