by Andrew Sinclair
An audit of accidents at speed camera sites before and after installation has found a decline in serious accidents.
Speed cameras are often introduced after a spate of accidents
Norfolk boasts a 67% drop and the local safety camera partnership claims this shows they work.
Anti-camera campaigners say they are often introduced after a "random" spate of accidents and justified because the level falls back to "normal".
As part of a week of features about transport, BBC Look East asked if speed cameras cut accidents.
PA Consultants carried out the national audit of speed cameras and Terry Marsh, in charge of the cameras in Suffolk, said he is sure their figures are right. He took me to the A12 near Saxmundham to show me some evidence.
"There are several bends close together here and this has always been a notorious accident black spot," he said.
"We reduced the speed limit to 50mph but that didn't work. Since we put in a camera the number of serious injuries has declined.
"In the three years before a camera was put up there had been three serious injury accidents - in the three years since there has not been any," said Mr Marsh.
But those opposed to speed cameras say these figures are based on statistical blips.
Paul Smith runs the Safe Speed website and said: "For some random reason there are four accidents in a year at a spot.
"In goes a speed camera but then for the next few years the number of accidents goes back to its previous level.
"Suddenly it can be claimed that before there was a camera there had been four accidents, now there is only one."
Those who have studied this subject independently, like Paul Pilkington from the University of the West of England, admit the data is limited but he says it is conclusive.
"All the evidence we have on speed cameras shows that when they're introduced into an area accidents, deaths and injuries do fall," he said.
"What we don't know is which type of camera is best - whether a mobile camera is better than a hidden camera."