COW ("Only Stwpd Cowz Txt N Drive")

Why it works

Cassie, a 17-year-old driver, sends a text at the wheel, drifts into oncoming traffic and causes a three-car crash on the outskirts of Tredegar that kills four people; the camera lingers on a girl's head slamming against a window and the blank stare of a baby in another car. Gwent Police and Tredegar Comprehensive School had set out to remake a joyriding film by local director Peter Watkins-Hughes, but the pupils insisted that texting while driving was the bigger danger and that the film had to be more shocking, violent and truthful. Made for about £10,000, its four-minute crash sequence went viral in 2009, passing four million YouTube views within weeks and reaching The New York Times as American states debated texting bans. It is studied as low-budget shock done with cinematic conviction, and as a flashpoint in the debate over gore in road-safety films. The clip was a trailer for a 30-minute drama due on BBC Wales, and by 2011 it had been seen more than seven million times.