Bob Brook said he would have died if he had got to hospital 30 minutes later following the collision between an InterCity passenger service and a fully-laden coal train near the North Yorkshire village of Great Heck which claimed the lives of 10 men.
A series of virtual events are being held on Sunday to mark the 20th anniversary of the collision on February 28 2001.
Mr Brook told BBC Look North: "My first awareness was lying in the bottom of the coach with somebody lying on my legs.
"I'm fairly lucky not to die. If I'd have been half an hour later into hospital I probably wouldn't have made it."
Mr Brook described how events of that day stayed with him, saying: "Doing anything other than sitting quietly at home was absolutely terrifying."
His wife, Chris Brook, said: "Obviously, total thankfulness that he survived.
"I did feel that he changed quite a bit. We don't really talk about it. I wouldn't even say that he's now the person that I married."
The accident claimed the lives of John Weddle, the GNER driver; Steve Dunn, the Freightliner driver, and eight other men - Steve Baldwin, Alan Ensor, Raymond Robson, Paul Taylor, Clive Vidgen, Barry Needham, Robert Shakespeare and Christopher Terry.
The tragedy happened after a GNER Newcastle to London passenger service struck a Land Rover which had careered off the M62 motorway and crashed onto the track.
The derailed passenger train was then hit by a Freightliner train carrying 1,600 tonnes of coal coming the other way, with a closing speed of more than 140mph.
Land Rover driver Gary Hart could not move his vehicle off the tracks and was calling the emergency services when the crash happened.
Hart had had little sleep the night before his vehicle veered off the motorway and plunged down an embankment, onto the East Coast mainline.
He denied falling asleep at the wheel but a jury found him guilty of 10 charges of causing death by dangerous driving. He was sentenced to five years in jail, serving around half that time.
Mr Brook said: "I can forgive him for making a mistake. I can't forgive him for not acknowledging he made a mistake.
"The whole way through he pretended he hadn't done anything wrong."
Online memorial events will be broadcast from Great Heck and Newcastle on Sunday morning and organisers say people around the world are expected to join in.
This will involve laying wreaths, readings and pausing as an LNER train passes Great Heck and sounds its horn as a tribute to those who died.
On Sunday afternoon, an online memorial service will be live-streamed from Selby Abbey, led by Canon John Weetman, Vicar of Selby Abbey, and the Reverend Peter Hibbs.
A commemorative candle will be lit for each of those who lost their lives.