Her Majesty's Inspector of Constabulary, which carried out the study, Road Policing and Traffic, found that forces in England and Wales operated different "secret" speed limits.
Lack of resources and over-worked staff are partly blamed by chief officers for allowing motorists to escape the law. Inefficient and marginalised policing roads policy was held responsible for the wide variations.
Colin Smith, the report's author, said policing of the roads had become a "Cinderella service", despite an average of 69 deaths on roads each week at an estimated cost of pounds 12.6bn a year to deal with the accidents.
The study of six forces - the Metropolitan Police, Kent, Lancashire, Norfolk, South Wales, and West Mercia - recommended targeting groups of offenders; "drink-drivers, speeders, born-again bikers [middle-aged men who buy motorbikes] or road ragers".
Mr Smith said that, at the moment, a driver prosecuted in one area could have gone unpunished if stopped in another.Reuse content