49 CFR §238.209

1. (a)Except as specified in § 238.201(b)—
   1. (1)The skin covering the forward-facing end of each locomotive, including a cab car and an MU locomotive, shall be:
      1. (i)Equivalent to a 1/2-inch steel plate with a yield strength of 25,000 pounds-per-square-inch—material of a higher yield strength may be used to decrease the required thickness of the material provided at least an equivalent level of strength is maintained;
      2. (ii)Designed to inhibit the entry of fluids into the occupied cab area of the equipment; and
      3. (iii)Affixed to the collision posts or other main vertical structural members of the forward end structure so as to add to the strength of the end structure.
   2. (2)As used in this paragraph (a), the term “skin” does not include forward-facing windows and doors.
2. (b)The forward end structure of a cab car or an MU locomotive may comply with the requirements of appendix F to this part in lieu of the requirements of either § 238.211 (Collision posts) or § 238.213 (Corner posts), or both, provided that the end structure is designed to protect the occupied volume for its full height, from the underframe to the anti-telescoping plate (if used) or roof rails.