More than half of fixed speed cameras in England and Wales do not work at any one time, according to a study dated January 2011.

More than half of fixed speed cameras in England and Wales do not work at any one time, according to a consumer watchdog.

A study by Which? also found that the chances of getting caught speeding vary dramatically from county to county, with all 60 Sussex cameras in operation while just 10% of Lancashire's 287 sites are ready to snap motorists.

Less than 47% of all fixed cameras are operational at any one time, Which? said, with most areas having more yellow boxes than actual cameras and rotating the working part at random or in response to speed and accident statistics.

The watchdog asked all 43 police authorities in England and Wales how many fixed speed camera housings they had and how many were in operation, under the Freedom of Information Act.

Dorset, Hertfordshire, Merseyside, Norfolk and Suffolk refused to answer, but the available results showed counties had between 10% and 100% of their cameras in operation. Durham said it used a single mobile camera because there was no need for fixed cameras anywhere in the county, while Cleveland, North Yorkshire and Wiltshire also did not operate any fixed sites.

Elsewhere, Cumbria Police had just 12 fixed cameras - one of the lowest totals in the investigation - but all were operational. Staffordshire Police had 263 speed camera housings but just 11% were in operation, while Avon and Somerset had 54 sites of which 94% were operational.

A Which? survey of 1,920 members found 47% of people thought speed cameras made the roads safer and 45% did not, while 83% believed they slowed drivers down only at specific locations.

Which? editor Martyn Hocking said: "Speed cameras in some areas are always operational, whereas in others there could be a one in 10 chance the camera you've passed isn't working. It really is a tale of two counties."

Peter Rodger, chief examiner with the Institute of Advanced Motorists, said: "Cameras cost a lot of money to install and maintain and for that reason there have always been more boxes than cameras. A yellow camera box that has no camera is totally effective if it achieves casualty reduction with no prosecution.

"One that catches large numbers of people but doesn't reduce casualties is doing nothing useful. A yellow box has a huge psychological impression on drivers, whether or not it is live, and it is the effect of this that is important, rather than whether the camera is recording."