General Knowledge · Communicating
Why must a bus, truck, or truck-tractor be equipped with a horn?
1.Federal equipment regulation requires a horn that gives an adequate, reliable warning signal to alert othersCorrect answer
2.It is required under federal rule only on vehicles that were manufactured after the year 2010, under an old grandfather clause
3.It substitutes entirely for having a set of functioning brake lights mounted on the rear of the vehicle
4.It is optional safety equipment that most trucking fleets only ever add voluntarily for driver convenience
Explanation
Federal equipment regulation requires every bus, truck, and truck-tractor to be equipped with a horn and actuating elements in condition to give an adequate and reliable warning signal, under 49 CFR 393.81, so the driver has a way to alert other road users to the vehicle's presence when needed. This is a genuine federal equipment mandate, not something limited to vehicles built after a certain year, and it is not a substitute for brake lights, which serve an entirely different function. It is also not merely a voluntary fleet add-on; the regulation itself requires it using mandatory language.
Source: 49 CFR 393.81
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