The analysis was carried out by Professor Richard Allsop of University College London following the release of speed camera data in 2011 as part of a government move to make speed camera operations more transparent to the public.

Analysis of data for 551 fixed speed cameras in 9 areas shows that on average the number of fatal and serious collisions in their vicinity fell by more than a quarter (27%) after their installation.

There was also an average reduction of 15% in personal injury collisions in the vicinity of the 551 cameras.

However the research also highlights 21 camera sites (in these areas) at which, or near which, the number of collisions appears to have risen enough to make the cameras worthy of investigation in case they have contributed to the increases.

The estimates for collision reduction were made allowing for the more general downward trend in the number of collisions in the 9 areas in recent years, and for the effect of regression to the mean at sites where collision numbers were unusually high in the period before the cameras were installed.

The study comes in the wake of the 2011 instruction from government that speed camera data going back to 1990, detailing accident statistics before and after fixed speed cameras were installed, be made publically available.

Since 2011 only a third (12 out of 36) of the organisations (a mixture of councils, police forces and safer roads partnerships) responsible for the figures have published the information in a format that complies with official Department for Transport guidance.

The RAC Foundation asked Professor Allsop to produce a guide for local authorities and other interested parties to help them interpret the data. As part of his work Professor Allsop studied data from nine of these authorities (with the data from one area being divided into two groups of cameras) and the results are as follows:

Professor Stephen Glaister, director of the RAC Foundation, said: ‘At the end of 2010 we published a report by Professor Richard Allsop which concluded that without speed cameras there would be around 800 more people killed or seriously injured each year at that time. Overall his new work reinforces those earlier conclusions, but crucially the study has also identified a number of camera sites in the vicinity of which collisions seem to have risen markedly. This may or may not be related to the cameras but warrants further investigation. Therefore, on the basis of this study, we have now written to eleven local authorities suggesting they examine the positioning and benefits of a total of 21 cameras.’

He added: ‘What is disappointing is that only a third of those bodies required to release the data have done so in a readily useable and consistent form.’