Okla. Stat. tit. 47, § 1-151
A steam engine, diesel, electric or other motor, with or without cars coupled thereto, operated upon rails.
Laws 1961, HB 556, p. 319, § 1-151, eff. September 1, 1961; Amended by Laws 2001, SB 539, c. 131, § 2, emerg. eff. July 1, 2001 (superseded document available).