Safe Driving Practices

Study questions with answers

12 sample Safe Driving Practices questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.

1. 1. What have tests shown about front-wheel braking on slippery surfaces?

   Correct answer: Skids caused by front braking are unlikely even on ice, so front braking helps everywhere.

   Braking at the front is beneficial in every condition; testing shows that front-wheel skids from braking are unlikely even on ice, so the control should stay set to 'normal.'

   Source: Section 5.1.13 - Front Brake Limiting Valve

2. 2. The safety relief valve in the first air tank is normally set to open at about what pressure?

   Correct answer: 150 psi.

   The safety relief valve, mounted in the first tank the compressor fills, usually opens at 150 psi to protect the system from excess pressure.

   Source: Section 5.1.6 - Safety Valve

3. 3. What does a supply pressure gauge tell the driver?

   Correct answer: The amount of pressure currently held in the storage tanks.

   The supply pressure gauge is connected to the tanks and shows how much air they currently hold; dual systems have one for each half or a single two-needle gauge.

   Source: Section 5.1.9 - Supply Pressure Gauges

4. 4. Why can the brakes still be applied several times even after the compressor quits pumping?

   Correct answer: Because the storage tanks hold a reserve of compressed air.

   The reservoirs store a reserve of compressed air, so the brakes can be worked several times even after a compressor that has quit pumping.

   Source: Section 5.1.3 - Air Storage Tanks

5. 5. If the air compressor carries its own oil supply, what should the driver do before setting out?

   Correct answer: Confirm that its oil level is adequate.

   A compressor with its own separate oil supply needs its oil level checked before driving, just like any other lubricated component.

   Source: Section 5.1.1 - Air Compressor

6. 6. If you must keep raising the application pressure just to hold the same speed, what is likely happening?

   Correct answer: The brakes are fading, so you should slow down and gear down.

   Needing more and more application pressure to maintain speed indicates the brakes are fading; the driver should slow down and shift to a lower gear (leaks, adjustment, or mechanical faults can also cause it).

   Source: Section 5.1.10 - Application Pressure Gauge

7. 7. When you press the pedal on an s-cam brake, what does the s-cam itself do?

   Correct answer: It rotates and forces the brake shoes apart against the drum.

   Air moves the push rod and slack adjuster, twisting the camshaft so the S-shaped cam spreads the shoes apart and presses them against the drum.

   Source: Section 5.1.8 - Foundation Brakes (S-cam)

8. 8. How large a crack in a brake drum makes it unfit for service during inspection?

   Correct answer: A crack longer than half the width of the friction area.

   A drum or disc is out of service once a crack runs beyond half the friction area's width; linings, too, must not be loose, oil-soaked, or worn dangerously thin.

   Source: Section 5.3.2 - Walk-around Inspection (drums, linings, hoses)

9. 9. If one half of a dual air brake system loses most of its pressure while driving, what results?

   Correct answer: Either the front or rear brakes lose full operation, so stopping takes longer.

   If one system runs very low, full braking is lost at either the front or the rear, so stopping takes longer; park the vehicle safely and get the air brakes repaired.

   Source: Section 5.2 - Dual Air Brake

10. 10. On a trailer equipped with ABS, where is the yellow malfunction lamp located?

    Correct answer: On the left side, at a front or rear corner.

    Trailers carry the yellow ABS malfunction lamp on the left side, at either the front or the rear corner; tractors, trucks and buses have theirs on the instrument panel.

    Source: Section 5.1.16 - Antilock Braking Systems (ABS)

11. 11. What feature is sometimes added to automatic tank drains for cold climates?

    Correct answer: Electric heating elements that stop the drain from freezing.

    Automatic drains expel water and oil on their own and can be fitted with electric heaters to keep the drain from freezing in cold weather.

    Source: Section 5.1.4 - Air Tank Drains

12. 12. During a walk-around, a manual s-cam slack adjuster likely needs adjustment if it moves more than about how far where the push rod attaches?

    Correct answer: About one inch.

    Pulling hard on the slack adjuster, if it moves more than roughly one inch where the push rod connects, it probably needs adjustment; too much slack makes the vehicle very hard to stop.

    Source: Section 5.3.2 - Walk-around Inspection (slack adjusters)