There is relatively* frequently a DRS loco at Dunkeld & Birnam, but I'm not sure I can work out why. If I had to guess I assume it's to rescue stranded broken down trains on the single track sections north of there, but why not have it at Perth where it could then also be used for the Aberdeen line more easily, and presumably closer to a driver (unless DRS conveniently have a driver who lives in Dunkeld!). Is there likely to be any other explanation?
* relatively is, of course, subjective - I notice it when I drive past but that might not mean it's there the majority of the time!
* relatively is, of course, subjective - I notice it when I drive past but that might not mean it's there the majority of the time!