Speeding drivers are being handed "three strikes and you're out" warnings during speed checks run by residents.

Across the county, residents have been spot-checking the speed of vehicles using Oxfordshire County Council's Speed Indicator Devices (SIDs).

They log registration numbers of offending cars and police post a warning letter to the driver. If the same vehicle is caught a second time, a further warning is sent.

And if it is spotted speeding a third time, details are passed to the police's roads policing department for further action, possibly including a hefty fine.

At least 152 warning letters have been sent to motorists across the county so far.

But police said no vehicle had been brought to their attention more than twice.

Supt Mick Doyle, head of roads policing, said: "The letter identifies the risks and issues created by excess speed and encourages all drivers to abide by the speed limit."

He added that if a vehicle was travelling at sufficient speed to constitute a "significant threat", details would be passed to the roads policing department for further action, even though initial warnings had not been sent.

Many of the sites for the checks are chosen after residents highlight speeding as a main priority during Neighbourhood Action Group meetings or surveys.

The letter sent to motorists says: "The driver should consider this letter to be a warning but should also be aware that details have been entered on to police records.

"Should your vehicle be detected speeding again in this, or any other Thames Valley SpeedWatch area, details will be passed on to the roads policing depart- ment for future targeted enforcement against your vehicle and possible prose- cution."

SIDs' recordings are not sufficiently accurate to be used as evidence in court.

The community scheme, called SpeedWatch, is organised by the county council.

So far, speed checks have been held in Jericho and Marston in Oxford, and in Eynsham, Kidlington, Carterton, Bicester and Bampton.

Paul Walters, the AA's head of traffic, said: "We've always been nervous about community speed watches.

"What if a resident notes down the number of a neighbour or even their wife? There could be problems. But we favour a warning before prosecution."

Cynthia Barlow, chairman of road crash victim support charity RoadPeace, said: "I would be happier if you weren't able to get one after another without anything happening. They should also take the chance to use these letters to tell the drivers how dangerous speeding is."

Paul Cullen, of the Life Begins at 20 campaign and Oxford Pedestrians' Association, said: "We support the community approach, but there are certain individuals who drive at high speeds and you need the law to deal with them."