This article was published in 2007, in Newsletter 70.
Cambridgeshire County Council has just approved its first permanent installation of average speed cameras. This innovation matters because it opens up the prospect of effective enforcement of speed limits. The cameras are to be installed on the road between Chatteris and Ramsey which runs alongside a local waterway – the Forty Foot Drain – where in recent years several drivers and passengers have been drowned after their cars left the road. Exceeding this road’s 50 mph speed limit has been a factor in a number of these cases.
Such cases bring out the fact that loss of control of motor vehicles through speeding is not a rare event on our roads. Obviously this is a risk not just for the vehicle’s occupants but also for other people, especially any pedestrians and cyclists who happen to be in the vicinity.
Average speed cameras (also known as SPECS cameras) work by measuring the time taken by vehicles to travel between two fixed camera sites which may be anything between 200 metres and 10 kilometres apart. Vehicles are identified by the Automatic Number Plate Recognition (ANPR) system. Such cameras are a major advance over the familiar single-site speed cameras because they offer an effective means of enforcing speed limits along a length of road rather than just at a single location.
Independent research sponsored by the Department for Transport has established the effectiveness of average speed cameras (as well as other types of speed camera) in reducing both speeds and injury accidents. The research has shown average speed cameras to be particularly effective in reducing excessive speeds, defined as 15 mph or more over the speed limit (paragraph 2.6).
For cyclists and pedestrians it is particularly important that the speed of motor vehicles is controlled effectively because small increments in speed result in substantial increases in serious injuries and deaths when they are hit by motor vehicles: 90% of people hit by a vehicle at 40 mph die, 20% at 30 mph and 2.5% at 20 mph (see Road Speed Reduction in Cambridge in Newsletter 59).
A 20 mph speed limit is being introduced in most of Cambridge’s historic city centre. We strongly support this but would like the zone to be larger than the County Council proposes (see The City Centre 20 mph Zone, Newsletter 60). Arguments against a larger zone have stressed the difficulties of enforcement. What average speed cameras offer is the possibility of effective enforcement without the necessity for road humps and other traffic-calming measures.
The Campaign has pressed for a 20 mph limit along Victoria Avenue, Maid’s Causeway and Newmarket Road up to the East Road roundabout. This route skirts the edge of the proposed city centre 20 mph zone. Our intention in pressing for this is to push forward the aims of Cambridge’s Core Traffic Scheme which include the provision of safer and more convenient routes for cyclists and the creation of better and safer environments for pedestrians. Such a limit would make this route safer and would enhance the attractions of the commons (Jesus Green, Butt Green and Midsummer Common) through which these roads pass and make them more readily accessible to pedestrians and cyclists. This limit could be enforced for through traffic by two average speed cameras, one sited at the beginning and the other at the end of this length of roadway (see Rising Cameras, Falling Bollards, Newsletter 67).
We are also seeking speed limit reductions in some other areas of the city where, in our view, present limits are too high and are intimidating or dangerous for cyclists and pedestrians. 20 mph zones are needed where there are high cyclist or pedestrian injury accident figures or to provide safe and convenient routes to schools. All areas of new development in Cambridge should, we believe, have 20 mph limits from the start.
There are two main obstacles to the creation of more rigorous speed limits and to the increased use of average speed cameras to enforce them. The first is the understandable but unacceptable caution of government, both nationally and locally. In August 2006 the Department for Transport published Setting Local Speed Limits which gives the latest government guidance. To its credit the DfT has developed a road management strategy with the commendable target of achieving a 40% reduction in the number of people killed or seriously injured on the roads by 2010 (see paragraph 15). They recognize the correlation between speed and accident frequency and severity.
For example they cite research indicating that each reduction by 1 mph in average speed reduces accident frequency by 5% (paragraph 17). However they ask that speed limits should be set at the average speed at which people drive along the road in question (paragraph 36) and that, in general, they should be enforced by road design and not just by speed limit enforcement. For 20 mph zones they require traffic calming measures and consultation with the local police force (paragraphs 75 and 79). Such requirements make it more difficult than it should be to introduce lower speed limits. Now that average speed cameras offer effective enforcement, traffic calming is much less necessary than it used to be.
Cambridge’s requirements for low speed limits are among the greatest in the UK. A city in which the proportion of cyclists is nearly twice as high as anywhere else in the country and in which the number of pedestrians is also unusually high should place particular emphasis on the control of motor vehicle speed. The latest government guidance helpfully states that, in considering what is an appropriate speed limit, ‘traffic composition (including existing and potential levels of pedestrian and cycle usage)’ is an important factor (paragraph 32). They continue ‘The needs of vulnerable road users must be fully taken into account in order to further encourage these modes of travel and improve their safety. Setting appropriate speed limits is a particularly important element in urban safety management with significant benefits for pedestrians and cyclists’ (paragraph 33).
The second main obstacle to the creation of more rigorous speed limits and to the increased use of average speed cameras to enforce them is cost. Current average speed cameras are expensive and this has been a principal reason for their slow introduction. The installation between Chatteris and Ramsey is to cost about £300,000. However, there are promising signs of less costly cameras in future. We understand that some of these are currently being evaluated.