Speed camera hotspots

A34, Bloxwich, 12 cameras in 3.2 miles, 3.8 per mile A411, Watford, 13 cameras in 4.2 miles, 3.1 per mile M25, Surrey, 48 cameras in 16 miles, 3 per mile Carmarthenshire, 7 cameras in 1.2 miles, 5.8 per mile

The survey was conducted by Morpheous, which manufactures an in-car speed camera detector.

Police have supported siting cameras for road safety reasons.

But Simon Wooding, spokesman for the AA in the Midlands, said: "Four per mile is quite extravagant, I only hope people are slowing down and these cameras are achieving their purpose.

"It's a shame people can't take their foot off the accelerator and need technology to slow them down.

"If speed restrictions can't be enforced, or people refuse to adhere to them, one of the most effective means of slowing motorists down is speed cameras."

Inspector Mark Riley, of Staffordshire Police, said: "If there are traffic safety issues then the police support the siting of speed cameras."

The number of cameras on the roads in England and Wales could triple over the next few years, from 4,000 to 12,000, as more police forces join the government's "cash for cameras" scheme.

Under the National Safety Camera Initiative, police forces are allowed to keep part of the revenue from fines for speeding to use for traffic safety.

Last week another 10 forces joined the scheme bringing the total to 25 out of the 43 police forces in England and Wales.