Code of Federal Regulations Title 49. Transportation § 49.213.334 Ballast;  general

(a) Transmit and distribute the load of the track and railroad rolling equipment to the subgrade;

(b) Restrain the track laterally, longitudinally, and vertically under dynamic loads imposed by railroad rolling equipment and thermal stress exerted by the rails;

(c) Provide adequate drainage for the track;  and

(d) Maintain proper track crosslevel, surface, and alinement.