One thing to know tho. If you start with a loco in the middle of the yard, and the yard has 10mph signs at its entry, the loco will default to 40mph until is passes a speed limit that says different.
So you can either start just outside the yard and enter it, passing the 10 mph sign or place a speed limit right in front of where the loco is parked, even using an invisible one if a visible one seems inappropriate.