Driver of ScotRail HST had only seconds to react, says RAIB
THE driver of ScotRail’s 0638 Aberdeen-Glasgow had under four seconds to react when the landslip at Carmont came into view on the morning of August 12 2020.
He applied the emergency brake one second before hitting the debris, but could do little more. RAIB’s reconstruction of the derailment that followed showed the train decelerating from 73mph to rest in 15 seconds and 240 metres.
Three seconds after derailing, the leading power car hit the parapet of Bridge 325, with the train moving at 60mph. It then hit the embankment on the far side of the bridge at around 45mph, according to RAIB.
Driver Brett McCollough died. So did conductor Donald Dinnie, who had been standing in the front vestibule of the leading coach (Coach D) behind the power car. The front of this coach, and the rear of the power car, were badly crushed when the train hit the parapet. This coach was the most damaged of the four in the train.
Passenger Christopher Stuchbury died when he was thrown from the leading vestibule of the second coach (C). This coach jack-knifed with the coach in front. Three other passengers were seriously hurt, two in the first coach who were thrown from it and one in the second coach who was thrown around inside it.
The remaining three passengers (one a ScotRail conductor) suffered minor injuries. Two were in the second coach and were thrown against its interior. The conductor was alone in the back half of the rear coach (A) and was injured when climbing out of the wreckage. There was no one in the third coach (B).
RAIB Deputy Chief Inspector Andrew Hall said: “If we look at the way this High Speed Train performed in this accident, in some ways it performed well and in other ways it performed less well. The ways in which it performed less well do relate to staying in line, remaining coupled, retaining the bogies and overriding.
“We’ve recommended that the industry needs to understand any
relative difference in risk between operating modern, crashworthy rolling stock, post-1994, or operating older stock such as HSTs because the first point in determining whether change is justified - as low as reasonably practicable risk - is to fully understand that risk.”
His “post-1994” comment relates to a change in crashworthiness standards, with trains built since then better able to withstand forces unleashed in derailments or collisions.
Hall said: “While it is not possible to be certain about what would have happened in a hypothetical situation with different rolling stock in the same accident, RAIB considers it more likely than not that the outcome would have been better if the train had been compliant with modern crashworthiness standards.”
RAIB drew attention in its report to the way the HST shed bogies from under its Mk 3 trailer coaches. All except the trailing bogie of the fourth and final coach detached. RAIB noted minimal damage to the coaches’ centre pivots, from which it concluded that the bogies were lost as the coach bodies lifted from them. Only gravity normally keeps them in place.
Their loss meant the first three coaches could slide and roll in an uncontrolled manner. Even derailed (so brakes no longer work) bogies would likely run through ballast and help slow a train, RAIB said. They increase the chance of coaches remaining upright and reduce the risk of jack-knifing, it added.
RAIB suggests stronger couplers between the train’s vehicles might have helped. It thinks they might have held the front power car to Coach D. “This might have been sufficient to keep the leading power car on the track for longer, increasing the likelihood of it completely traversing the bridge still coupled to Coach D,” the report says.
It also looked at what effect stronger lifeguards might have had. They protect the leading wheels from small obstacles and in modern trains have coped with hitting landslip debris. HST lifeguards have half the strength of modern ones, but RAIB concluded that it didn’t have enough evidence to show that modern lifeguards would have prevented the derailment.
Likewise, guard rails would have made little difference. They are fitted to the track to contain derailed wheels on the approach to tunnel portals or bridge parapets. They typically extend 18 metres beyond the ends of a bridge, but RAIB notes that the HST’s leading wheels had deviated too far for them to be affected at a point 35 metres from the bridge. NR installed them at Bridge 325 during rebuilding work after the accident.