Well, you certainly need ONE.
Staging yard, arrival/departure yard.
Something to set up your wayfreights FROM and bring the result back TO.
Usually, it’s the shed, or storage area.
Mine is heated, lit, coffee pot, single track in, 5 tracks across, plus 3 storage tracks on the far wall past the turn table, one accessible from Track 5, two off the table itself.
Then there is the turntable with 4 double-length tracks and one single-length to the side, and then there is the 3-track “maintenance” yard next to the inbound/outbound track, with Track 1 and Track 2 of the primary yard feeding the turntable, so when the cars get set out for ops, locos can come in and out around each other, plus a crossover in the middle, when some yay-who goes to the head and leaves his loco just sitting on Track 1.
Depends on how big the rr is, how many cars and locos, how much is set out (over 130 pieces of rolling stock, 75 or so are “set out” initially) and what you want to have “ready”.
I have an intermediate yard at Laurel, 4 tracks across, three are “through” tracks, one stub, the stub gets setouts from various locations for the through freight to take “down the hill”.
The three through tracks are necessary for holding trains waiting for the Lilac Branch.
I also have 10 passing sidings, altho only 8 are used as such in sessions.
That’s why we can run 20 separate trains at once.
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