Engineers are investigating a steep slope in Scotland after a rock fall derailed a passenger train on Sunday.
The incident happened shortly before 9pm and left a carriage suspended over a 15m drop in a rural part of Argyll. All 60 passengers on the 6.20pm Glasgow to Oban train were rescued but eight people were taken to hospital with minor injuries.
The train’s driver Willie Dickson is reported to have seen “two huge rocks” on the track before the collision, which happened on a steep stretch of slope historically prone to rock falls. Debris is also understood to have fallen onto a road downslope of the railway.
Network Rail confirmed that there is a 6.4km long boulder screen 20m upslope of the affected section of railway that sends a signal if a rock fall event occurs. This tensioned wire fence comprises 10 steel wires supported by steel and timber posts typically at between 2.7m and 3.6m apart. The wires are at between 230mm to 250mm spacings.
The stretch along the Pass of Brander runs beneath the slopes of Ben Cruachan, which rise steeply above the track. Rockfall hazards have been a concern since the line opened 130 years ago.
However, there was no fence breach and no signal sent so investigators are looking at whether boulders fell onto the track from the section below the barrier.
Recent research was carried out by the Transport Research Laboratory (TRL) for Transport Scotland following a number of landslides along the road network. This work identified the slope as potentially hazardous.
“There is a long-term history of movement in this area. It is susceptible to debris flow and there is a history of rock falls.”
Mike Winter, TRL
“Our work [in the Scotland Road Network Landslides Study] highlighted it as being a potential susceptibility area,” TRL Scotland regional director Mike Winter told NCE.
“There is a long-term history of movement in this area. It is susceptible to debris flow and there is a history of rock falls. The slopes are very, very steep, and are steeper towards the bottom, which is characteristic of glaciations.”
However, Winter said mitigation was not automatically required, because the work can be very expensive.
“No work has been done in the area but that is not to say that work won’t be done in the future,” he said.
“Events change perceptions.”
Network Rail could not confirm whether additional remediation work was being planned for the slope but said that slope and track monitoring had taken place recently and were well within its inspections programme.
“It is too early at this point to say what has caused the incident and whether we need to change the maintenance regime as a result,” said Network Rail in a statement. “That is something that the RAIB [Rail Accident Investigation Branch] investigation and our own inquiries will determine.”
It added that it would be “very difficult” to eradicate the risk entirely.