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Air Brakes · Air Brake Warning and Control Devices

In a vehicle equipped with air brakes, which control is used to set the parking brake?

1.A dedicated control shaped like a diamond and colored yellow, pulled outward to set the spring brakes for parkingCorrect answer
2.The same foot brake pedal used for ordinary everyday stops, held down by a foot-operated mechanical latch device
3.A hydraulic lever mounted near the driver's seat that clamps the wheels directly without using any air pressure at all
4.The ignition switch, which is wired to apply the parking brake automatically and immediately whenever the engine shuts off

Explanation

An air brake vehicle sets its parking brake with its own dedicated control, usually shaped like a diamond and colored yellow, mounted on the dash; pulling it out releases the air that has been holding the spring brakes off, letting the springs apply and hold the vehicle in place. 49 CFR 383.111(b)(1) requires CDL applicants to know general air brake system nomenclature, the required-knowledge area this control falls under; the specific shape and color of the control is standard driver-training content from the manual, not spelled out in the CFR paragraph itself. The ordinary brake pedal is wrong because it is a separate service brake control, not the parking brake, and pedal-locking latches are not how air brake systems set a parking brake. A hydraulic lever is wrong because air brake systems apply spring pressure through the same foundation brakes already in the vehicle, not a separate hydraulic clamping mechanism. Automatically applying at the ignition switch is wrong because the parking brake control must be operated on its own, it does not happen automatically just because the engine is shut off.

Source: 49 CFR 383.111(b)(1)

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