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]