An Oxford Mail investigation with a speed gun found almost half of motorists were putting lives in danger by speeding in and around the city.

We found 47 per cent of drivers who passed us were exceeding the speed limit, with one going at 57mph in Bayswater Road, a 30mph zone.

The Royal Association for the Prevention of Accidents (RoSPA) called for drivers who flout speeding restrictions to see our findings as a "wake-up call" and slow down.

Crime reporter Jo Duckles and reporter Anna Dowdeswell went to speeding hotspots with Oxfordshire County Council's speed indication device operator, Bryan Hunt.

We used a speed laser gun for traffic going in one direction at each location and were out on the road between 10am and 3pm to avoid the slowing effect of rush hour.

We also used a speed indication device, which tells drivers what speed they are doing, smiling at them if they are on or below the speed limit and frowning if they are above it.

We visited four locations for 30 minutes each Cumnor Hill; Marston Ferry Road, near The Cherwell School; Lime Walk, Headington; and Bayswater Road, near Oxford Crematorium.

Out of a total of 476 cars that drove past, 224 were driving above the speed limit, with more than 50 per cent speeding in Marston Ferry Road and 68 per cent in Bayswater Road.

In Lime Walk, a residential street where parked cars cause a natural chicane, we caught only one driver above 30mph, but Mr Hunt said householders there were calling for the speed limit to be reduced to 20mph.

It was there that two drivers, including a clergyman, stopped to ask us what we were doing, and told us to "keep up the good work".

Mr Hunt said: "One accident victim going through the health system probably costs more than what our department costs to run per year.

"I would say these findings are typical of what I would normally find."

Roger Vincent, a spokesman for the Royal Society for the Prevention of Accidents (RoSPA), welcomed our investigation.

He said: "We hope this will be a wake-up call for some motorists to watch their speed.

"We would like to see more done to help motorists, better signing, and also would like car manufacturers to make speedometers and displays more clear so it's easier for people to see how fast they are travelling and stay within the limit."

Dan Campsall, of the Thames Valley Safer Roads Partnership, said our figure of nearly 50 per cent was consistent with the national average.

He said: "Five years ago, it was 66 per cent, which means we are making some headway."

He said intervention from Oxfordshire County Council with speed indication devices and vehicle-activated signs had helped.

He said: "In some places, we have engineering measures, chicanes, and speed humps and we have education campaigns with Fox FM delivering Slow Down radio commercials.

"We have done work throughout the year with Six Television, producing documentaries talking about the dangers of speed."

Our speeding investigation comes after spot checks we carried out last month found 19 drivers using mobile telephones along Botley Road in 90 minutes.

The first check, carried out from 8.45-9.45am near the railway station, found six motorists talking on their phones and another five texting amounting to two per cent of the 510 vehicles counted travelling into the city centre.

In the second check, between 5.40pm and 6.10pm opposite Halfords in Botley Road, seven people were spotted talking on their phones, with one driver texting 1.8 per cent of the 440 vehicles counted heading towards Botley.