The HADECS3 (Highways Agency Digital Enforcement Camera System) cameras are designed to enforce speeds on the motorways that are set up to use the hard shoulder permanently or temporarily as a running lane.

However, the police could choose to use the new verge-mounted cameras – which are grey instead of yellow and can monitor all four lanes of traffic – on normal stretches of motorway.

The cameras are a replacement for the gantry-mounted HADECS2, which are currently used to enforce variable speed limits. These cameras, however, require white lanes on the road, whereas the new model does not.

RAC technical director David Bizley said: ‘We know that enforcement is needed on existing managed motorways with variable speed limits when the limit is set below the national speed limit of 70mph. The new generation of smart motorways with all lanes running and no hard shoulder have far fewer gantries so enforcement of variable speed limits requires verge-mounted cameras such as HADECS3.’

He added: ‘Static Gatso-style speed cameras have become a regular fixture on our roads and are normally located in accident black-spots for safety reasons rather than being used for general speed limit enforcement. One of the key concerns about static speed cameras is there potential to create a dangerous ‘stop start’ driving style caused by motorists suddenly slowing down when they spot them.

‘This is often seen on existing managed motorways with some drivers exceeding the limit between gantry-mounted enforcement cameras and braking sharply as they approach the next gantry. No doubt this will also be the case with verge-mounted HADECS3 cameras. One might expect this behaviour to lead to accidents though we are unclear whether the evidence supports this. The existing HADECS2 cameras require white line markings on the road which are also known to cause motorists to brake so their removal might possibly reduce the risk of accidents.

‘The decision not to paint these new cameras yellow may possibly be influenced by a desire to discourage this “stop start” behaviour, but there can be no doubt that motorists will soon learn where to expect cameras regardless of their colour.’

Bizley also said that the new cameras provide a good basis to revisit the 80mph trial.

‘We have been supportive of trialling an 80mph speed limits on some sections of motorway where construction and usage patterns are such that the benefits to users would offset any detrimental safety or environmental impact. Unfortunately, the Government has stated there are now no plans to do such a trial which is disappointing.

‘If the new HADECS3 cameras are to be used more generally we think that this will result in better adherence to speed limits. One of the objections to an 80mph limit was that motorists would be more likely to travel at 90mph or more. But with better enforcement, it would be appropriate to revisit the 80mph motorway debate given that the majority of motorists support raising the speed limit on motorways.

‘The RAC Report on Motoring 2013 voiced drivers’ frustrations that, despite Government announcements some time ago of plans for trialling of an 80mph limit so that the benefits and disadvantages could be quantified, nothing has happened to date and there are real doubts as to whether the current ministers have the will to proceed.

‘Only 20% of motorists surveyed said that the current 70mph motorway speed limit should never be broken and 65% of motorists admit to breaking this limit while 92% of all drivers consider themselves to be law-abiding.’