§ 393.89 Buses, driveshaft protection.
Any driveshaft extending lengthways under the floor of the passenger compartment of a bus shall be protected by means of at least one guard or bracket at that end of the shaft which is provided with a sliding connection (spline or other such device) to prevent the whipping of the shaft in the event of failure thereof or of any of its component parts. A shaft contained within a torque tube shall not require any such device.
[33 FR 19735, Dec. 25, 1968, as amended at 53 FR 49402, Dec. 7, 1988]