Grabovskis, who had got on the 16:40 Corby train, said: “I was about to board the first carriage, but there were too many people because the train only had four carriages, so at the last second I moved to the last carriage.”
He said he had gone flying when the collision happened, passed out and woke up on the floor to see people “covered in blood” and screaming.
“It was one of the most terrifying moments of my life, and I know how fortunate I am to be here today,” he added.
Stephenson said the crash site was “quite difficult to get to”.
He said: “The overhead wires need to be removed, a crane needs access to remove train carriageways and there’s been so much damage to the rails that about 600m of track needs to be replaced before the overhead wires can be replaced and then the track can reopen.
“The teams will work at pace but there’s an awful lot of work to do.”
A doctor, who sustained multiple fractures in the collision, remained on the train to care for some of the most seriously injured passengers.
The GP, from Bedford, stayed at the scene until they were taken to hospital.
Commuters arriving at Bedford station on Monday said railway staff had been doing their best to offer support.
Network Rail said the line was expected to remain closed between Bedford and Luton for the rest of the week, until 28 June.
There will be no GTR services north of Luton and no EMR services south of Bedford, with a limited rail replacement bus service in operation between Luton and Bedford.