Indiana Code Title 8. Utilities and Transportation § 8-8-1-4

Sec. 4. It shall be unlawful for any such common carrier to use any locomotive, tender, car or similar vehicle used in the movement of state traffic, that is not provided with draw bars of standard height;  to wit, standard gauge cars thirty-four and one-half (34 1/2 ) inches;  narrow gauge cars twenty-six (26) inches;  measured perpendicularly from the level of the tops of the rails to the centers of the draw bars;  the maximum variation from such standard heights between draw bars of empty and loaded cars shall be three (3) inches.