Service & Storage for Diesel Engines

[railohio]

North American main line locomotives do not spend much time idle. When traffic is moderate or heavy, they are brought in, serviced, and sent out on the next train to depart. During time of recession, they are gathered up and placed out-of-the way tracks or in outlying terminals:

DeadLineJanesvilleWI11-3-12 by railohio, on Flickr

If you're storing the locomotives, you just need one track, or more in parallel, with the locomotives coupled together.