The report by Road Safety Analysis comes as a number of local authorities have decided to switch their cameras off to save money, and focused on comparing collisions on roads near speed cameras in Northamptonshire before and after the switch-off.

Report author Richard Owen said the results show that collisions actually reduced in the post-switch-off period and that the variation in reductions against the Northamptonshire average of all other roads is not significant. It could therefore be said that the cameras have continued to ‘work’ despite their inactivity.

The report added: “The main reason for this could be that drivers have not changed their behaviour at camera sites over the last four years. Anecdotal evidence from residents suggests that the vast majority of drivers still stick to the limit when passing camera sites, although there may be a small majority who choose to flout the law in the knowledge a ticket will not arrive in the post.

“Motorists may still be under the impression that the cameras are working as the housings are regularly maintained and not covered in bags stating they are out of use. Previous, unpublished research by the author has shown that bagged cameras have an immediate impact on vehicles speeds, which return to normal once the bags are removed.

“The most significant outcome from this analysis is that fixed speed cameras do not need to be loaded regularly to achieve casualty reduction. This could significantly change how cameras are operated nationally with the potential to reduce costs associated with the loading and processing of offences. The savings could be used to support more widespread deployment of enforcement cameras in more locations with lower loading ratios.”