Documentary series following the traffic police as they enforce the law on some of Britain's busiest and most dangerous roads. The Traffic Cops in South Wales attend a head-on smash in a contra-flow on the M4, involving a party of youngsters enjoying a day out in a chauffeur-driven limousine. They also apprehend some thirteen-year-old would-be car thieves, and send in the dogs to foil an audacious night-time heist.