Police are still searching for clues as to why the car at the centre of Saturday's rail crash in Berkshire was stopped on a level crossing.
Mr Drysdale's parents said they didn't know why it had happened
They said they owed it to the families of all the victims, including that of car driver Brian Drysdale, 48, to find out how he came to be there.
Police have examined his mobile phone - found near the scene - and are not ruling out suicide.
Mr Drysdale's colleagues said they were "shocked" by news of his involvement.
The chef, who lived in Reading, left work less than an hour before the derailment, in which he and six others died.
A spokesman for Wokefield Park golf complex, near Mortimer, Berkshire, confirmed Mr Drysdale had been at work on Saturday and left at around 5.30pm.
He had been employed there for the last 15 months, and was described as a "valued member of the catering team".
Mr Drysdale's route between work and his home in Reading would have taken him close to the crash site, near Ufton Nervet, police believe.
A First Great Western train travelling from London Paddington to Plymouth ploughed at high speed into Mr Drysdale's parked silver Mazda on the crossing at about 1815 GMT on Saturday.
The BBC's Rachel Wright said reports suggested Mr Drysdale's car was on the track for quite some time before the crash, and was re-positioned shortly before the impact.
Mr Drysdale's parents Keith and Etta, both in their 70s, said they were shocked by the accident.
Their solicitor Michael Akehurst said: "The family have
already given whatever assistance they can offer to help the official inquiries...and are willing to provide any further help during the course of these lengthy investigations.
"They have no information on the circumstances surrounding their son's death."
Family friend Dayline Vickers, 44, said the couple were "just heartbroken".
"Etta said she had lost her son but she knew that other people have lost their loved ones as well."
British Transport Police Deputy Chief Constable Andy Trotter has said suicide was still being considered as a line of inquiry.
"For that driver to drive on to the crossing and leave the vehicle there, obviously it is one line of inquiry that we have had," he said.
But he emphasised police had not closed their minds to other explanations, such as a mechanical defect in the car.
The chef left work less than an hour before the tragedy
Officers were looking into Mr Drysdale's background, and his actions around the time of the crash, he said.
Family liaison officers have been assigned to speak to those close to the chef whom, according to reports, was not married and had no children.
His sister-in-law Shirley Sadler told the London Evening Standard she couldn't believe Mr Drysdale would willingly harm other people.
Investigators have been gathering parts of the car which were scattered over 225ft (69 metres), while work continues to remove wrecked carriages from the site.
Although his mobile phone had been found at the scene, there was no suggestion Mr Drysdale was using it in the minutes leading up to the smash, he added.
He confirmed there were no CCTV cameras covering the scene but said this was normal practice on a quiet rural crossing.