The Commissioner of Police has consistently taken the view that the police should, as far as possible, by the use of patrol cars, encourage a high standard of behaviour on the part of road users, and accordingly the traffic patrol cars in the Metropolitan Police district normally show a prominent "Police" sign, and their crews wear uniform. Experience has shown, however, that it is necessary to supplement this by other methods, including fixed controls, for detecting and dealing with drivers who do not observe the law, more especially on stretches of road with a bad accident record.