On the M5 near Birmingham, patrollers Dave and Martyn must shut down the motorway when a car fire gets dangerously out of control and the vehicle is discovered to be packed with explosive contents. A high-speed smash between an HGV and a small car leaves a student nurse shaken but uninjured, and a young commuter's hopes of getting to work on time are blown when a 40-ton truck side swipes him off a roundabout and writes off his car