Drivers in Derbyshire are among the least likely to be caught speeding in England and Wales, new data reveals.
The RAC Foundation warns that differing priorities among police forces lead to huge regional disparities in catching speeders.
Derbyshire Constabulary detected 10,480 speeding drivers between April 2017 and March 2018, a recent study carried out by the RAC Foundation shows.
That's a rate of 10 offences per 1,000 people in the area, one of the lowest in England and Wales.
Nearly all the infractions in Derbyshire were captured by speed cameras.
Across England and Wales, police caught 2.3 million drivers speeding over the year – a rate of 40 per 1,000.
Avon and Somerset had the highest rate, with 120 drivers per 1,000. Gwent had the lowest, with less than one offence per 1,000.
Chief Constable Anthony Bangham, the National Police Chiefs’ Council lead for roads policing, said priorities are decided by individual forces.
He said: "We are concerned over the consistency of speed enforcement across different police forces and we continue to review how we could bring greater clarity to the public.
"However, it’s important to emphasise that each force area has a varied road infrastructure which makes direct comparisons difficult.
“Whilst forces are issued with general guidance in relation to speed enforcement, our model of local accountability within policing means each chief constable has ultimate discretion over operational priorities".
Steve Gooding, director of the RAC Foundation, warned that any targeted crackdown on speeding could be repeated if reckless attitudes re-emerge.
He said: "There will be varied reasons to explain some of the differences between areas, such as geographical area, road type and traffic volume. But a lot of it will come down to local policing priorities.
"It is the job of Police and Crime Commissioners and chief constables to target resources appropriately, recognising the issues of greatest local concern.
"Changes and variations in the numbers of offences detected will reflect not just driver behaviour, but also the extent of enforcement activity in any one year."
Of those offenders caught in 2018-17 by Derbyshire Constabulary, 85% were given a fine.
Speed awareness courses were nearly unused – only 1% of the offenders were sent to them, compared to 44% in England and Wales.
A further 1% of the offences in Derbyshire resulted in court action, while 13% were cancelled.
Provisional plans agreed by the EU mean that new cars sold in the UK from 2022 will have default devices which stop them breaking the speed limit.
The Department for Transport said new rules would apply to the UK despite Brexit.