Wales train crash: leaf fall and digital signalling are possible areas of inquiry

The fatal collision occurred at low speed – seemingly less than 20mph – and there is a possibility that at least one train was out of control. Photograph: Ian Cooper/PA Media

The fatal collision of two trains between Talerddig and Llanbrynmair in rural Wales on Monday evening is, in many respects, unique in Britain’s recent rail experience. No head-on crash had been recorded this century, and there had only been one fatal passenger train crash since 2007 in the UK.

Inspectors from the Rail Accident Investigation Branch (RAIB), who arrived on the scene in Powys on Monday night and resumed in daylight, are likely to release an early report this week.