Track is rarely elevated to
equilibrium elevation
because not all trains will
be moving at equilibrium
speed through the curve.
Furthermore, to reduce
both the maximum
allowable superelevation along with a reduction of underbalance provides a margin for
maintenance. Superelevation should be applied in 1/4-inch increments in most
situations. In some situations, increments may be reduced to 1/8 inch if it can be
determined that construction and maintenance equipment can establish and maintain
such a tolerance. Even if it is determined that no superelevation is required for a curve,
it is generally accepted practice to superelevate all curves a minimum amount (1/2 to
3/4 of an inch). Each railway will have its own standards for superelevation and
underbalance, which should be used unless directed otherwise.