The use of average-speed cameras has been found to cut the number of crashes resulting in death or serious injury by more than one-third.

Research for the RAC Foundation by Road Safety Analysis found that, in mean terms, the number of fatal and serious collisions decreased by 36% on a stretch of road after average-speed cameras were introduced. The average reduction in personal injury collisions of all severities was found to be 16%.

Steve Gooding, director at the RAC Foundation, said: “There is cause for optimism about the overall collision reduction benefits of average-speed cameras.

“Taking account of overall trends, permanent average-speed camera sites were found to, on average, reduce injury collisions, particularly those of highest severity.”

Speed-limit enforcement, in particular the use of camera-based prosecution systems, has been a contentious issue for some years. Cameras were originally introduced at speeding or crash hotspots, but are now increasingly installed for other reasons, such as tackling traffic flow, air quality and vehicle noise.

Gooding said: “In 2010, the RAC Foundation published a report which analysed the effectiveness of speed cameras. The report focused on the use of ‘spot’ cameras, the most widely used camera technology at the time, finding that cameras could be a valuable part of the road safety armoury.

“Technology has now moved on and more authorities are looking to average-speed cameras – systems that measure the speed of a vehicle over a stretch of road – to ensure speed limit compliance. It therefore seemed timely to commission a similarly rigorous look at how these systems are performing.”

By the end of 2015 there were at least 50 stretches of road in Great Britain permanently covered by average-speed cameras, keeping a total of 255 miles under observation.

The 50 stretches range in length from less than half a mile in Nottingham to 99 miles on the A9 between Dunblane and Inverness in Scotland. Many of these sections of road will be monitored by several sets of cameras.

The first stretch of road to become permanently managed by average-speed cameras was the A6514 ring road in Nottingham in 2000.

MPs on the Transport Committee have suggested that more average-speed cameras should be deployed to catch motorists who drive too fast. At least 12 systems were installed last year alone.

Speed cameras, said the Transport Committee’s report on road traffic enforcement, are an “important and effective part of the technology toolkit” and, if enforcement is going to be effective, greater use of technology is essential.

It said that average-speed cameras are generally “better received by motorists than traditional fixed-speed cameras”, but existing schemes should be assessed for their long-term effectiveness and, based on this, Highways England should develop best practice for their deployment.

One reason for the increase in usage has been the cut in installation costs of permanent average-speed cameras. The figure is now typically around £100,000 per mile, compared with around £1.5m per mile in the early 2000s.

Some of the older spot speed cameras – commonly known as Gatso cameras – have been around for 25 years and still use 35mm film. As they come to the end of their operating lives they are starting to be replaced, in some cases with average-speed systems.

In August this year, for example, West Midlands Police turned on average-speed camera systems on eight stretches of roads in Birmingham and Solihull. This was three years after the old-style, wet-film, Gatso cameras were turned off.

The wider roll-out of speed cameras could prove costly for some company car drivers. Nine out of ten (88%) admitted to speeding on motorways, according to the RAC Report on Motoring (www.fleetnews.co.uk: October 6).