Gareth Dennis said the “High Speed Trains” (HSTs), which are based on a 50-year-old design, should no longer operate because of the lack of protection they offered in a crash compared to more modern trains, including for drivers.
While other companies such as LNER have scrapped their fleets, ScotRail operator Abellio has acquired and refurbished the trains for use on inter-city services.
One of the trains derailed last August after it hit stones washed onto the tracks by heavy rain, killing the driver, Brett McCullough, 45, conductor Donald Dinnie, 58, and a passenger Christopher Stuchbury, 62.
The six other people aboard the train – five passengers and a conductor travelling to join another train – were injured.
An interim report into the incident at Carmont, south west of Stonehaven, by the UK Department for Transport’s rail accident investigation branch (RAIB), said its main areas of investigation included the “crashworthiness of rail vehicles in high energy accidents”.
Mr Dennis told The Scotsman: “The HST has no modern crashworthiness features – none at all.
"I think it’s pretty appalling that we’re still using those trains in front line service.”
He said of particular concern was the lack of protection for drivers, which he described as “unacceptable”.
The engineer said of the HST on his latest Rail Natter podcast: "I adore it but it's a museum piece.
"It shouldn't be running in regular service any more.
"Drivers should not be operating these trains. It is as simple as that.
"The HST cab is essentially an upturned bath tub mounted facing outwards with a driver inside it.
"There is zero crash structure for the cab – absolutely zero crashworthiness whatsoever.
"Zero protection for the driver.
"All there is the base of the front of the HST with a fibreglass shell over the front.
"There is no crash structure at all.
"I'm amazed they have not been blacklisted as a result of Carmont."
Referring to crashworthiness being investigated by the RAIB, Mr Dennis said: "I hope the RAIB do not pull their punches."
He also compared the incident to the crash of a more modern Virgin Trains’ Pendolino at Grayrigg, near Kendal in Cumbria in 2007, in which only one person had died despite the train being heavier and travelling faster.
Mr Dennis told The Scotsman he hoped Transport Scotland would now plan for an earlier replacement of the HSTs than the current 2030 target date.
He said: “By raising the lack of crashworthiness in these vehicles, there’s a chance that might accelerate some of those discussions.
"My hope is it will be in the next few years.”
He added: “Railways remain the safest form of overland transit by a very long way, but that doesn’t mean the rail industry shouldn’t be striving for better safety.”
ScotRail said it was unable to comment pending the RAIB investigation.
The drivers’ union Aslef and Transport Scotland declined to comment.
A ScotRail High Speed Train driver writes:
"How do I feel about driving the HST?
"I used to love it, HSTs are much more fun to drive.
"You have so much power at your fingertips, it's not even comparable to diesel multiple units - these trains are incredibly fast, and yet, slow to react to your inputs.
"There's a delay after taking power, a delay after applying the brake, and a delay taking the brake off.
"Never mind the fact they are much heavier than the trains we used to drive.
"This is a machine that demands a lot more of you as a driver, it forces you to respect it.
"To become a driver, you have to spend months in the classroom.
"One thing is hammered into you over and over again, and that is safety.
"We are taught about the Swiss cheese theory of safety.
"Every system of safety is imperfect – we can imagine these systems as slices of Swiss cheese.
"A beam of light representing a failure of safety may get through the holes in one, but with enough layers, an accident will be blocked before it can happen.
"I knew I was safe flying along at 100mph, there were so many layers of protection preventing anything happening to my train, what was there to worry about?
"Well, I'd get my answer.
"Carmont changed everything.
"Looking at those images I could barely believe my eyes, the devastation, the crushed carriages, the power car buried in the trees.
"Then I saw it, the cab was gone, there was nothing left, it had completely sheared off.
"I started to look into the HST and realised just how unprotected the driver is.
"I can't even adequately express how little protection there is for us.
"It's zero, there is nothing.
"Now when I'm driving along at 100mph, over 200 tonnes at my back, I can think of nothing else except the literal fibreglass shell surrounding me.
"There may be plenty of layers of Swiss cheese preventing a crash: signalling, infrastructure, training, processes, but that slice labelled "cab integrity" isn't a slice of cheese, it's the clear plastic wrapper with nothing inside.
"A tree across the line just at the right angle, a trampoline pole blown on to the line in high winds, or that car that's ploughed onto a level crossing just as my train comes screaming round the corner, imagine any of these hitting a fibreglass shell travelling 100mph.
"Nobody deserves to head to work and not come home safe at the end of the day.
"Like Brett, like Donald, and like Chris, I am a parent, and every single time I get into the cab of a HST, I think about whether this will be the one that stops me coming home to my kids.
"So how do I feel about driving the HST?
"Angry, terrified, powerless."