They have flashing lights, fast cars, yellow jackets and they must be obeyed. But a new generation of law enforcers who can pull you over on the motorway are not police but controversial "civilian traffic officers".
In an effort to free police time to tackle more serious crime, officials from the government's Highways Agency have been given powers to direct traffic, close roads, clear up accidents and rescue stricken motorists.
But motoring organisations fear their presence will be an excuse for cutbacks in genuine traffic police. The Police Federation has questioned their value for money and is doubtful about their effectiveness after just eight weeks' basic training.