Two men gave chase and helped ensure that no one was hurt as the machine wheeled itself off down the hill.
Rail accident investigators report that on Friday 8th June 2018, the road-rail maintenance vehicle ran away towards Bradford Interchange terminal station, with operator and machine controller in hot pursuit, shouting warnings to other workers in the vicinity.
The maintenance vehicle was a mobile elevating working platform (MEWP) that was equipped with both rubber wheels for road running and steel rail wheels for running on rail tracks. That night, it was intended to be used for examination work on a section of track that was under night-time possession.
The runaway started at the Britannia Street road-rail access point, which provides a flat surface allowing road-rail vehicles to be manoeuvred on to the track. This access point is on a section of railway which slopes downwards at a 1-in-50 gradient towards the station before running onto level track as it enters the platforms.
Shortly after 01:30 hrs the MEWP was being transferred from its rubber tyres to its steel wheels. During this manoeuvre, known as on-tracking, the machine operator was controlling the machine using a remote control unit, connected to the machine by a cable. As the rail wheels were lowered onto the track, the MEWP started to run down the gradient towards the station where it stopped about 340 metres from the access point (and before reaching the buffers at the end of the platform).
No-one was on board the MEWP as it started to run away. The machine operator and machine controller attempted to stop the runaway. They were unable to do so, but they kept up with the machine during its travel to warn other staff working in the vicinity.
The Rail Accident Investigation Branch (RAIB) said that initial evidence suggests that the runaway occurred because the on-tracking was not carried out correctly and the rail wheel brakes, intended to hold the vehicle on the gradient, provided insufficient brake force to do so.
The RAIB’s investigation will explore the full sequence of events that led to the runaway and the factors influencing the actions of those involved in the on-tracking operation.
It will also look into the actual capability of the rail wheel brakes, the rail-conversion and maintenance history of the MEWP and the standards and design approval processes that were applied to this type of MEWP.