Why? Why dedicate such an insignificant function just for the depots? I mean its not like there will be animals or tresspasers at the depots. Do drivers use the depot whistle at the night as a more silent alternative to the horn?
Trespassers no, but other workers yes, it's a warning that you'll start to move, and people living near depots would go mad with constant loud horns
There’s me thinking the depot whistle was to warn off badgers and poachers without waking the neighbourhood when it was for the safety of employees all along I call it the despot whistle and use it alert the passengers of a potential evil dictator in the vicinity
Noise abatement is a thing here, especially as new fleets often have new depots that may be near residential areas. The new Scarborough depot has been all but forced to close because of residents complains. The residents were fine with trains passing, but when some abandoned sidings were converted into a new fueling and cleaning point with 3 or 4 class 68s running in hotel mode all night the complaints started - even at idle a 68 is audible 2-3 miles from the railway! The depot layout means the trains have to be shunted so shutting down the engines wasn't an option