On Wednesday 24 May a manually propelled track trolley being used during engineering works on the Circle Line of London Underground ran away down a gradient of 1 in 70 and collided with another, stationary, trolley. A warning had been given and all staff were clear of the line. There were no injuries.
The immediate cause of the incident was that the trolley brakes failed to stop the trolley when they were applied. Causal factors were the failure to carry out prescribed checks of the trolley before use and a modification to the brake system that reduced its effectiveness. There were four factors contributing to the incident, and the underlying cause was identified as the widespread unauthorised modification of brakes allowed and encouraged by this design of trolley.
RAIB has made nine recommendations aimed at:
- the design, acceptance and maintenance of track trolleys;
- the training of Track Trolley Operators (TTOs);
- the management of sites where track trolleys are used;
- the reporting of incidents on the London Underground network.
Response to recommendations:
RAIB will periodically update the status of recommendations as reported to us by the relevant safety authority or public body. RAIB may add comment, particularly if we have concerns regarding these responses.