Tennessee CDL — Air Brakes Practice Test 1

1.What is a "wig wag" low air pressure warning device?

A mechanical arm that drops into view when pressure drops below 55 psiA gauge that counts the seconds of pressure buildupA valve that vents excess pressure at 150 psiA knob you pull to set the parking brakes

2.How do you test that the parking brake will hold?

Rev the engine to full throttle in neutralSet it, then in a low gear gently try to ease forward against itRoll downhill and release it suddenlyPump the brake pedal ten times quickly

3.If the air compressor has its own separate oil supply, what should you do before driving?

Check the compressor's oil levelDrain the oil completely so it does not overheatAdd alcohol to the compressor housingDisconnect the v-belt to protect the seals

4.Does ABS guarantee a shorter stopping distance?

Yes; it always cuts stopping distance roughly in halfYes; it stops the vehicle instantly with no lagNo; it actually makes every stop longerNo; its main value is keeping the vehicle under control during hard braking

5.Why should you avoid pressing the brake pedal while the spring brakes are already applied?

The combined spring and air forces could damage the brakesIt would drain the tanks below the cut-in pressureIt would release the parking brakes unexpectedlyIt would trigger the safety valve to open

6.If one side of a dual air system loses most of its pressure, what happens to your stopping?

Nothing changes; the other system covers all brakesIt takes longer to stop because some brakes are not working fullyThe vehicle stops faster than normalThe parking brakes take over automatically at speed

7.How does the stop light switch warn drivers behind you that you are braking?

It sounds a horn as the pedal movesIt drops a wig wag arm behind the cabAn air-operated electric switch turns on the brake lightsIt flashes the low pressure warning light

8.Why is it important to drain the water that collects in the air tanks?

In freezing weather, that trapped water can turn to ice and knock the brakes outWater makes the air gauge read too highWater speeds up the compressor beyond its cut-out pointWater sets off the low air pressure warning by mistake

9.What is "brake lag" in an air brake system?

The time the driver takes to notice a hazardThe distance the vehicle rolls before you reactThe time the compressor needs to reach cut-outThe short delay for air to reach the brakes after you press the pedal

10.Why can the brakes still be applied several times even after the air compressor quits working?

The storage tanks keep a reserve of compressed air on handThe spring brakes generate their own air supplyThe governor pumps air directly to the wheelsThe alcohol evaporator produces backup pressure