Pennsylvania CDL — Air Brakes Practice Test 3

1.Where is the ABS malfunction lamp located on a trailer?

On the rear bumper at the centerOn the instrument panel inside the cabOn the left side, at a front or rear cornerBehind the tractor's grille

2.At 55 mph in good conditions, the total stopping distance for an air brake vehicle is greater than about how many feet?

About 100 feetAbout 200 feetAbout 500 feetMore than 300 feet

3.What is a 'wig wag'?

A lever that gradually applies the spring brakesA mechanical arm that drops into view when air pressure falls below 55 psiA valve that limits pressure to the front brakesA gauge needle that shows applied pressure

4.Which statement about ABS is correct?

It prevents wheel lockup in hard braking but may not shorten the stopping distanceIt always shortens your stopping distanceIt replaces your normal service brakesIt runs continuously the whole time the vehicle is moving

5.If a vehicle has an alcohol evaporator, is daily draining of the air tanks still needed?

No, the evaporator removes all the moisture on its ownOnly when the weather is below freezingYes, unless the tanks have automatic drain valvesOnly when the compressor carries its own separate oil supply

6.On large buses, at roughly what pressure do the low-pressure warning devices commonly activate?

20 to 30 psiRight at 55 psiAbout 80 to 85 psi120 to 140 psi

7.In the snubbing technique, once you have braked to about 5 mph below your safe speed, what do you do next?

Hold steady brake pressure for the rest of the gradeShift into a higher gear and coastSet the parking brake to hold the lower speedLet off the brakes, then reapply once you return to your safe speed

8.What is 'brake lag' on an air brake system?

The brief delay while air moves through the lines before the brakes take holdThe time it takes the driver to spot a hazardThe distance traveled after the wheels lock upThe pause before the compressor cuts in

9.Why should you avoid pressing the brake pedal while the spring brakes are set?

The combined force of the springs and the air pressure could damage the brakesIt will empty the tanks instantlyIt makes the governor cut in earlyIt shuts off the ABS

10.A visible low-air-pressure warning must come on before tank pressure drops below what level?

55 psi100 psi20 psi85 psi