Railroad optimum design for grades is 0.5% or less, though up to 1.5% is acceptable in certain circumstances. Steeper grades result in continual reduction in train speed and can actually cause a train to stall if the grade is too steep, or require the use of additional locomotives, which is a major operating cost.

Horizontal curvature is not nearly as critical, though it can affect train speed and handling. The degree of curvature and desired train speed will impact the amount of superelevation used. Consecutive curves also require the design of a tangent length of track between curves to prevent the train from rocking, which can result in derailments.