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Reducing speed for smoother and safer roads

Contrary to what people may think, a faster speed doesn’t always mean more cars can drive on a stretch of road…

In fact, the more the number of vehicles increases, the more a higher speed becomes problematic. The recommended safety distances are no longer sufficient, slower vehicles disrupt traffic flow, and certain vehicles changing lanes force other drivers to reduce their speed. Usually we then see an “accordion” effect in the traffic, or even a traffic jam pure and simple.

Whereas varying our speed can actually increase the capacity of the road. Driving at a slower speed on motorways and dual carriageways is a great way of reducing inter-vehicular distance and therefore limiting congestion and jams. Numerous experiments in dynamic speed regulation have been carried out thanks to Egis in France and in Europe, in particular in Great Britain on the M25 ring road around London, jointly managed by Egis and its British partners (Balfour Beatty and Atkins).


On the M25 in London, the system works
Known as the London Orbital, the M25 is the circular motorway that runs around Greater London, characterised by its numerous intersections. At 188 km long, it is the second longest ring road in Europe, after the one in Berlin (196 km) and the busiest road in the whole of the UK. 


The M25 was the first English motorway to test out speed regulation in 1995, followed by the national “Smart Motorways” programme (GBP 6 billion) launched in 2014 by the UK government. Now, Europe’s second longest ring road is fully equipped with dynamic speed panels and cameras to control the 200,000 vehicles a day driving on the busiest sections. And to prevent the English from seeing the M25 as “the world’s biggest car park”, various prevention campaigns have been broadcast on the BBC to remind users that it is sometimes better to slightly reduce your speed to allow traffic to become more fluid.” Laurent Charles Nicolas, M25 project director for Egis