Mo. Rev. Stat. § 389.795

In cases in which the motor carrier and railroad safety division of the department of economic development finds the same to be practical and necessary for safety of railroad employees, bridges and trestles, over and upon which railroad trains are operated, shall include as a part thereof, safe and suitable walkway and handrail on one side only of such bridge or trestle, and such handrail shall be located at the outer edge of said walkway and shall provide a clearance of not less than eight feet, six inches, from the center line of the nearest track, measured at right angles thereto.