49 CFR § 213.323 - Track gage.

§ 213.323 Track gage.

(a) Gage is measured between the heads of the rails at right-angles to the rails in a plane five-eighths of an inch below the top of the rail head.

(b) Gage shall be within the limits prescribed in the following table:

Class of track The gage must be at least— But not more than— The change of gage within 31 feet must not be greater than—
Class 6 track 4′8″ 4′9 1/4 3/4
Class 7 track 4′8″ 4′9 1/4 1/2
Class 8 track 4′8″ 4′9 1/4 1/2
Class 9 track 4′8 1/4 4′9 1/4 1/2
[63 FR 34029, June 22, 1998, as amended at 78 FR 16104, Mar. 13, 2013]