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.
– Perry Meade
There was very quickly a second impact from behind, which was worse than the first one.
At the point of the second impact I was trying to get out of my seat to move across to get out of the passenger side, as it wasn't safe to get out of the driver side.
The second hit was extremely violent and it was if the truck was being shunted violently from left to right, like someone had grabbed it and given it a good shake.
I was lifted out of my seat on to the dashboard and back into my seat again.
I was disorientated and I went to climb out of the passenger side when we were hit for a third time and I was thrown against the dashboard.
This impact wasn't as violent as the second one and it was more of a rocking type motion - it almost felt like it wasn't a direct hit.
David Thomson, who was driving a Volvo S40, said series of collisions happened very quickly after he entered the thick fog.
– David Thompson
Within a few seconds of entering this are of reduced visibility there was a series of rapid collisions.
I'm not sure if I hit a vehicle or a vehicle hit me but the airbags went off.
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.
– Kevin Faulkner
I had to make a decision and I recall other impacts happening and fires starting so I decided to exit my vehicle for fear of being trapped.
I had no idea where we were and how long the emergency services would be. I could see the fire getting bigger and my fear was that the fire would engulf my vehicle.
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"
– Peter Hynds
The smoke was extremely thick and I could not see through it.
I have driven through mist and fog but never anything like this.
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:-