THE derailment of a Scotrail HST set at Dalwhinnie in the early hours of April 10 was caused by a signalling fault, an RAIB statement concludes.
The five-car set, known as HA19, was being operated as an overnight test train between Perth and Tomatin, using power cars Nos. 43012 and 43015 to check stepping distances, so there were no passengers on board; just five crew, who were uninjured.
The train had left Perth at 23.10, and was booked to call at all stations in each direction, arriving at Tomatin at 02.08.
It was returning south on time at 02.12 and running some 50 mins early on its way back to Perth when the derailment of a bogie on the last trailer and both on the rear power car took place. It occurred on a crossover at the south end of the Dalwhinnie station limits at around 03.03.