Over 250mi of road in Great Britain is monitored by average speed check cameras, a research has found.

The research for RAC Foundation by Road Safety Analysis has identified 50 road stretches that are continuously monitored by cameras.

These stretches range from a quarter mile on Tower Bridge in London to 99 miles on the A9 between Dunblane and Inverness in Scotland.

"Unsurprisingly, the indications are that compliance with the speed limit through stretches of road managed by average speed cameras is high, but the acid test is whether accident and casualty rates have also fallen."

A6514 Ring Road in Nottingham was the first stretch that was completely monitored by average speed cameras in 2000.

Last year, 12 camera systems were installed.

In the next phase, Road Safety Analysis will conduct a study for RAC Foundation to ascertain the effectiveness of cameras in terms of reducing casualties by comparing pre-installation data with post installation data.

RAC Foundation director Steve Gooding said: "Average speed cameras are becoming a more common fixture on Britain’s roads.

"Unsurprisingly, the indications are that compliance with the speed limit through stretches of road managed by average speed cameras is high, but the acid test is whether accident and casualty rates have also fallen.

"That is what the next part of this research project should tell us.

"Rightly or wrongly many motorists perceive the current ‘spot’ speed cameras to be more about raising revenue for the Treasury than saving lives, but average speed cameras have greater potential to bring drivers on side.

"Clearly a high-compliance rate means a very low-penalty rate and hence both road safety and drivers wallets could benefit from greater use of these systems in appropriate places."