Failings over runaway rail vehicle at Glasgow Queen Street
An accident where a rail worker was badly hurt by a runaway maintenance vehicle has been blamed on operator failure and brake design flaws.
The road rail vehicle (RRV) ran away as it was being transferred to the tracks in Glasgow on 21 April last year.
It crashed through scaffolding, injuring a worker, before coming to a stop at Queen Street Station.
The Rail Accident Investigation Branch (RAIB) has made four recommendations to improve safety when using the vehicle.
No-one was on board the RRV when it ran away at about 03:00 at the Keppochhill road-rail access point.
The vehicle ran through the tunnel and struck two scaffolds that were being used for maintenance work on the tunnel walls.
A male worker on one of the scaffolds was thrown to the ground and suffered severe injuries to his shoulder.
The RRV came to a stop, as the track levelled out, about 20 metres short of the buffer stop at platform five in Queen Street Station, after travelling a total distance of about 1.1 miles (1.8km).
In its report, the RAIB notes a variety of reasons for the accident.
"The machine operator put the machine into the position where only the rail wheel holding brake was acting to prevent movement, contrary to the on-tracking procedure in which he was trained," it stated.
"The machine operator was unable to operate the correct controls to apply braking by either fully raising or fully lowering the rail wheels when the RRV was moving."
Concentrating on the RRV, the RAIB noted: "The RRV was not fitted with any physical means of preventing the machine operator from putting it into the position where only the rail wheel holding brake was acting to prevent movement."
The report went on: "Deficiencies in the design and set-up of the rail wheel holding brake meant that it was inadequate to hold the RRV on the gradient."
It also stated: "The design calculations for the rail wheel holding brake assumed a higher coefficient of friction between the brake pads and the wheel than was available in practice."
The RAIB also found that the set-up of the braking system was inadequate.
"The RRV rail wheel holding brakes were not set up to provide sufficient braking force to prevent a runaway on a 1 in 41 gradient and there was no maintenance instruction requiring appropriate set-up," it stated.
It also noted: "One of the RRV brake cylinder springs had been assembled incorrectly; this is a possible causal factor."
Other failures identified were:
- the testing regime for the RRV rail wheel holding brakes did not identify shortcomings in the design of these brakes;
- the manufacturer's quality assurance processes were inadequate to identify the deficiencies in the rail wheel holding brake design;
- the approval process did not examine the specification or effectiveness of the rail wheel holding brake;
- the RRV lighting was not illuminated as it ran down the gradient;
- an interlock intended to prevent release of the rail wheel holding brake when the rail wheels were not fully deployed was not always effective;
- the machine operator was not briefed about the gradient; and
- the machine operator was not tested for drugs immediately after the accident.
The RAIB said the industry had to learn that the current rail vehicle approval process did not cover all aspects of rail vehicle performance.
It also made four recommendations covering quality assurance, safety audits, brake testing and lighting in relation to Network Rail and Rexquote, the firm that converted the RRV from a road vehicle.