Okla. Stat. tit. 40 § 188
On and after April 15, 1958, it shall be unlawful for any person, firm or corporation operating or controlling any railroad running through or within the State of Oklahoma and engaged in the business of a common carrier to operate a track motor car, or transport its employees in a track motor car, which is not equipped with a substantial top for the protection of said employees from rain, snow, sleet and hail, and equipped with a transparent windshield sufficient in width and height to protect said employees therefrom, which windshield shall be of safety glass. Such a motor car shall also be equipped with an electric windshield wiper that will remove rain, snow and other moisture from the windshield thereof, and said windshield wiper shall be so devised that the driver of said motor car can start or stop said windshield wiper while he is driving the same.
Okla. Stat. tit. 40, § 188