Intelligent motorway signs smooth journey to the coast

15 July 2009

Motorway signs that automatically read the road ahead are being used to make journeys easier and safer as thousands of holidaymakers head for the coast.

The signs encourage drivers to slow down gradually if there is congestion ahead, which means queues are more likely to disappear and traffic keeps moving at a steady rate.

“Stop-start traffic is not only more dangerous, it reduces the capacity of the motorway,” explains Highways Agency director of information Denise Plumpton. “These signs are just one example of the technology being used to keep traffic on the move this summer.”

Around 3,000 variable message signs are now used by the Highways Agency to manage England’s network of motorways and major trunk roads. On a typical holiday journey from Birmingham to Devon and Cornwall more than a hundred signs are available to flash up important messages.

Among the most frequent are the ‘MIDAS’ signs (Motorway Incident Detection and Automatic Signalling). These use sensors buried in the road surface to automatically detect slow-moving traffic and warn traffic further back – effectively increasing the ‘view’ of the road from a few hundred metres to several miles ahead. Instead of drivers reacting to the brake lights of cars in front, which creates stop-start traffic, vehicles slow down more gradually and delay times are reduced.

Sometimes this means that when the signs warn of a “queue ahead”, the queue will actually have dispersed by the time drivers reach the point of the original problem.

Actual journey time displayed on overhead signs

Another type of sign, called Travel Time Variable Message Signs, use monitoring equipment to measure the actual time taken by vehicles on a particular stretch of motorway.

For example, a sign on the M5 at Exeter displays the current time it is taking vehicles to reach Bodmin via the A30, 65 miles further ahead.

“These have proved very popular because they give accurate journey time information direct to road users,” says Denise Plumpton.

The messages on all variable message signs can be read on the Highways Agency website highways.gov.uk/traffic. This has an easy-to-navigate map facility showing how traffic is flowing and live information about any delays or incidents. Users can even check the view from thousands of CCTV cameras and get updates on their mobile phone when they are away from their PC.

As motorists head off for summer holidays or days out this summer, the Highways Agency is urging drivers to plan their journey and make sure their car is well-prepared. The advice to families includes checking the route and travel conditions before they set off, servicing the car regularly to reduce the chance of breakdown and always to carry an emergency kit. As the weather so far this summer has ranged from heatwave to downpour, the Agency is advising people to pack drinking water in case they get held up in the heat and warm, waterproof clothing in case they break down and need to take refuge away from the traffic in bad weather.