Okla. Stat. tit. 66 § 251
Except as to Sections 6, 9 and 18, the provisions of this act shall apply only to cabooses used on main-line trains, except that within four (4) years of the effective date of this act all cabooses in the State of Oklahoma shall be in compliance with this act, except the act shall not apply to cabooses used as rider cars in yard transfer movements having a one-way route mileage of fifty (50) miles or less; and, except the requirement outline in Section 5 of this act shall apply only to main-line through trains, and the four (4) year provision set to above shall not apply thereto. The provisions of Sections 2, 3, 4 and 5 hereof shall not apply to cabooses presently operated by railroads having less than one hundred (100) miles of main and branch line trackage; provided, however, that any additional cabooses acquired by said railroads shall comply with all of the provisions of this act.
No caboose shall be used in service subsequent to one (1) year after the effective date of this act unless it complies with Sections 3, 6, 8, 9, 10, 11, 12, 13, 14, 15, and 18 hereof. No caboose shall be used in service subsequent to two (2) years after the effective date of this act unless it complies with Sections 2, 4, 5 and 7 hereof. The Corporation Commission of the State of Oklahoma may, for good cause shown, extend the limitation of time allowed for compliance herewith.
Okla. Stat. tit. 66, § 251