Though AREMA has some general guidance for alignment design, each railway usually
has its own design guidelines, which complement and expand the AREMA
recommendations. Sometimes, a less restrictive guideline from another entity can be
employed to solve the design problem. Other times, a specific project constraint can
be changed to allow for the exception. Other times, its more complicated, and the
designer must understand how a train is going to perform to be able to make an
educated decision. The following are brief discussions of some of the concepts which
must be considered when evaluating how the most common guidelines were
established