§393.44 — Front brake lines, protection On every bus, if equipped with air brakes, the braking system shall be so constructed that in the event any brake line to any of the front wheels is broken, the driver can apply the brakes on the rear wheels despite such breakage. The means used to apply the brakes may be located forward of the driver's seat as long as it can be operated manually by the driver when the driver is properly restrained by any seat belt assembly provided for use. Every bus shall meet this requirement or comply with the regulations in effect at the time of its manufacture.
[53 FR 49400, Dec. 7, 1988]
§393.44 — DOT Regulatory Guidance
Question 1: Does the term "rear wheels" include the tag axle on a bus/motorcoach? Guidance: Yes. The braking system on a bus/motorcoach must be constructed so that if any brake line to either front wheel is broken, the driver can apply the brakes to all of the wheels on each rear axle.