The start mentioned here is impassable now. The gate at the railway station is locked and the car park mentioned has a phone that you have to ring the ‘train conductor’ to get permission to cross the tracks. It is denied.
Better is to turn at the 24 hour fuel station in Dalwhinnie and head to the railway line. About 300 m down this road is an ‘underpass’ that you can park near (about room for 8 cars).
Once through the underpass, you can easily pick up the trail again.