Nevertheless, Raib says there are still some significant gaps in existing safety arrangements. Raib has also identified some important areas of learning and made 74 recommendations to improve railway safety. In 2015 Raib was deployed to 32 accidents and incidents, started 21 investigations and one joint investigation with its French counterpart, and issued three safety bulletins and five urgent safety advice notices.

"It's very encouraging that the overall safety performance of the railway industry remains strong," says Raib's chief inspector, Mr Simon French. "However, continuation of this performance is dependent on vigilance and a willingness to address the types of issues that are identified by our investigations."

Raib says it has identified a number of recurrent concerns, particularly associated with the safety of track workers, the maintenance of track quality, the condition of some freight trains and the safety of passengers when boarding and alighting from trains.

"We have investigated several events which could easily have resulted in very serious accidents, including a track gang's narrow escape from a train travelling at 157km/h and a high-speed train derailing after striking a large section of masonry bridge parapet that had been pushed onto the track by a reversing lorry," French says.

"These events, and a number of recent catastrophic accidents in Europe, highlight why thorough and impartial accident investigation continues to play an important role in helping the railway industry to identify, and then close, gaps in the railway's safety defences."