Drivers have told an inquest of their horror at being involved in one of the worst British motorway pile-ups in living memory.
Within seconds of entering a wall of thick fog - described by some drivers as a "white curtain" or "emulsion" - they collided, leaving seven people dead and 51 injured.
34 vehicles were involved in a series of crashes on the northbound carriageway of the M5 near Taunton on 3 November 2011.
TNT lorry driver Perry Meade told the hearing today how his vehicle was struck three times in just five seconds.
Mr Meade had seen brake lights in front of him so had stopped his lorry and was just about to apply his handbrake when he was struck from behind.
David Thomson, who was driving a Volvo S40, said series of collisions happened very quickly after he entered the thick fog.
Roger Neno, who was behind the wheel of a Vauxhall Insignia saloon, said he saw brake lights of a lorry in front of him and managed to stop before hitting it.
Kevin Faulkner described the fog as a "white out" in front of him and suddenly was in collision with other vehicles.
Mr Faulkner, from Devon, said he was trapped inside his BMW X1, and a man - who he did not know - tried to open his door with a crowbar. He was eventually rescued from his car by the fire service.
Peter Davey, a collision investigator, said that accounts from witnesses to the length of the fog - described in court as an "area of reduced visibility" - differed but in his view it must have been more than 110 metres in length.
He said he come to that conclusion after examining various witness statements from survivors.
Peter Hynds, who was driving an Iceland lorry to Swindon, described becoming "confused and disorientated" after "looking into a scene of complete darkness"
Mr Hynds said he saw a stationary Land Rover in front of him and desperately tried to stop but could not in time.
He then turned off his ignition and seconds later his lorry was struck from behind.
David Woodland reports:-