Signals & Pavement Markings

Study questions with answers

7 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. How does the air brake system warn drivers behind you that you are braking?

   Correct answer: An air-operated electric switch turns on the brake lights

   A stop light switch, an electric switch triggered by air pressure, lights the brake lamps when you apply the air brakes.

   Source: Connecticut CDL Manual, Section 5.1.12 (Stop Light Switch)

2. 2. A visible low air pressure warning must appear before tank pressure drops below what level?

   Correct answer: 55 psi

   On most vehicles the warning you can see has to activate before the tanks fall under 55 psi (older units use one half the governor cut-out).

   Source: Connecticut CDL Manual, Section 5.1.11 (Low Air Pressure Warning)

3. 3. The application pressure gauge shows you need more and more pressure to maintain the same speed. What does that indicate?

   Correct answer: The brakes are fading

   Needing steadily more application pressure to hold a speed is a sign the brakes are fading; slow down and drop to a lower gear. Out-of-adjustment brakes, leaks, or mechanical faults can also cause it.

   Source: Connecticut CDL Manual, Section 5.1.10 (Application Pressure Gauge)

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

   Correct answer: On the instrument panel

   Tractors, trucks, and buses show the amber ABS warning lamp on the dash; trailers instead place it on the left side, at the front or rear corner.

   Source: Connecticut CDL Manual, Section 5.1.16 (Antilock Braking Systems)

5. 5. What does a 'wig wag' low-pressure warning do?

   Correct answer: It drops a mechanical arm into the driver's view when pressure is low

   The wig wag lowers a mechanical arm into sight when system pressure falls below 55 psi; an automatic one lifts back out of view once pressure rises above that level.

   Source: Connecticut CDL Manual, Section 5.1.11 (Low Air Pressure Warning)

6. 6. What does the supply pressure gauge tell the driver?

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

   Every air brake vehicle has a gauge tied to the tank showing how much pressure is stored; a dual system uses one for each half or a single gauge with two needles.

   Source: Connecticut CDL Manual, Section 5.1.9 (Supply Pressure Gauges)

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

   Correct answer: At 80 to 85 psi

   While most vehicles warn below 55 psi, it is common for big buses to signal low pressure at around 80 to 85 psi.

   Source: Connecticut CDL Manual, Section 5.1.11 (Low Air Pressure Warning)