July 13, 2020 | Susan Napier-Sewell

What caused a runaway locomotive in Beddgelert, North Wales

The diesel locomotive was unable to stop as it descended a steep gradient into Beddgelert station

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At approximately 09:17 am, on April 16, 2019, a diesel locomotive was unable to stop as it descended a steep gradient into Beddgelert station on the Welsh Highland Railway, Gwynedd. After passing through the station at around 10 mph (16 km/h), the locomotive passed a signal at danger (S.P.A.D.; running a red light) and then entered a single line section without authority. The driver tried various ways of applying more braking effort but was unable to slow the locomotive down. After traveling for approximately 1.7 km, the locomotive came to a halt when the gradient leveled out. The driver was uninjured, and no other train was on the line at the time.

The incident occurred because the locomotive’s brakes had been modified in a way that limited the movement of the brake blocks

This—the state of the adjustment of the brakes—and the wet conditions of the day prevented the brakes from applying the necessary brake force to slow the locomotive down. The issue with the brake system modification had remained undetected during the 18 years since the modification was made.

The RAIB (Rail Accident Investigation Branch) investigation found that the change to the locomotive’s brakes had not been adequately documented or controlled. RAIB observed that, although not causal to the incident, the locomotive did not have a documented brake inspection procedure, and the ‘deadman’ safety system was not enabled on the locomotive when the runaway occurred. RAIB also observed that the railway’s investigations of its incidents could be improved to better understand underlying systemic issues.


As a result of its investigation, RAIB has made three recommendations for the Festiniog Railway Company that relate to:

  • improving its management of engineering change
  • ensuring its maintenance processes are documented and controlled
  • the use of the “deadman” safety system

A fourth RAIB recommendation is addressed to the Heritage Railway Association to promote the distribution of this report’s findings to other heritage railways.

Lessons learned

RAIB has also identified three learning points, reminding heritage railways of the importance of:

  • carefully assessing, checking, and documenting safety-critical modifications
  • understanding the risks associated with all safety-critical systems and assessing existing control measures and dependence on human performance
  • a thorough investigation of safety incidents, which can help to ensure that risk mitigation measures are appropriate and proportionate

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