Signals & Pavement Markings

Study questions with answers

6 sample Signals & Pavement Markings questions with the correct answer, a short explanation, and the official handbook reference. Read through them, then take the quiz above.

1. 1. What is the purpose of the stop light switch in an air brake system?

   Correct answer: To light the brake lamps whenever you apply the brakes

   The stop light switch is an air-operated electric switch that lights the brake lamps so the drivers behind you know you are braking.

   Source: Section 5.1.12 - Stop Light Switch

2. 2. How does a "wig wag" low-pressure warning device work?

   Correct answer: It drops a mechanical arm into the driver's view when pressure falls below 55 psi

   A wig wag lowers a mechanical arm into your line of sight once pressure drops under 55 psi; the automatic version lifts back out of view when pressure climbs above that level.

   Source: Section 5.1.11 - Low Air Pressure Warning

3. 3. What information does a supply pressure gauge give the driver?

   Correct answer: How much air pressure is stored in the tanks

   The supply gauge, fitted to every air brake vehicle, shows the amount of pressure held in the tanks; a dual system uses one gauge per half or a two-needle gauge.

   Source: Section 5.1.9 - Supply Pressure Gauges

4. 4. On a tractor, truck, or bus, where is the ABS malfunction lamp located?

   Correct answer: On the instrument panel

   Powered units show a yellow ABS malfunction lamp on the dash; trailers instead carry theirs on the left side, at either a front or rear corner.

   Source: Section 5.1.16 - Antilock Braking Systems (ABS)

5. 5. Below what tank pressure must the low air pressure warning signal come on?

   Correct answer: 55 psi

   A visible warning must activate before tank pressure drops under 55 psi (or half the governor cut-out on older vehicles); it is usually a red light, sometimes with a buzzer.

   Source: Section 5.1.11 - Low Air Pressure Warning

6. 6. On a vehicle with an application pressure gauge, needing more and more pressure to hold a steady speed indicates what?

   Correct answer: The brakes are fading

   Having to apply increasing pressure just to maintain speed means the brakes are fading; the manual advises slowing down and dropping into a lower gear.

   Source: Section 5.1.10 - Application Pressure Gauge