Jim, superelevation is used on main track curves, to allow trains to operate at a faster speed, and to control wear on the inside edges of the rail, by managing lateral forces. The speed listed in the timetable is the balancing speed for that curve.
At low speeds, superelevation does more harm than good, as it increases lateral force by shifting most of the weight onto the low rail, wearing the wheel flanges and the low rail disproportionately. Even where there is, say, a 60 MPH super elevated curve paralleled by a 20 MPH siding, the siding will typically have no superelevation.
Yards, no. Superelevation would cause rail wear and plate-cut ties, and enhance opportunities for rolling the low rail when starting to pull a long cut of cars out of the track. Most yard ties are not the best on the railroad, and the least lateral force applied to them, the more sleep the Trainmaster gets.
