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. On a typical air brake vehicle, the low air pressure warning you can see must switch on before tank pressure drops below what level?

   Correct answer: 60 psi

   A visible low-pressure warning is required and must come on before the pressure in the tanks falls under 60 psi (older vehicles may instead use half the governor cut-out pressure).

   Source: Michigan CDL Manual — Section 5.1.11: Low Air Pressure Warning

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

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

   Tractors, trucks, and buses show the ABS malfunction lamp on the instrument panel, while trailers place the yellow lamp on the left side, either at the front or the rear corner.

   Source: Michigan CDL Manual — Section 5.1.16: Antilock Braking Systems (ABS)

3. 3. How does an air brake vehicle switch on its brake lights to warn drivers behind it?

   Correct answer: An electric switch triggered by air pressure when you apply the brakes

   An air-pressure-operated electric switch closes when you press the brakes, lighting the stop lamps so following drivers know you are slowing.

   Source: Michigan CDL Manual — Section 5.1.12: Stop Light Switch

4. 4. On a vehicle with a dual air brake system, how is tank pressure shown?

   Correct answer: A separate gauge for each half, or one gauge with two needles

   Because a dual system has two independent halves, each half gets its own supply gauge, or the two readings share a single gauge with two needles.

   Source: Michigan CDL Manual — Section 5.1.9: Supply Pressure Gauges

5. 5. You find you must keep raising application pressure to hold a steady speed. What is the application pressure gauge warning you about?

   Correct answer: The brakes are fading, so you should slow down and drop to a lower gear

   Needing more and more pressure to maintain the same speed points to fading brakes; the right response is to slow down and select a lower gear (brakes out of adjustment, leaks, or mechanical faults can also cause it).

   Source: Michigan CDL Manual — Section 5.1.10: Application Pressure Gauge

6. 6. What does the supply pressure gauge on an air brake vehicle tell the driver?

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

   Every air brake vehicle has a supply gauge tied to the reservoirs so the driver can read how much pressure the tanks are holding.

   Source: Michigan CDL Manual — Section 5.1.9: Supply Pressure Gauges

7. 7. What is a "wig wag" on an air brake vehicle?

   Correct answer: A mechanical arm that drops into the driver's view when system pressure falls below about 60 psi

   The wig wag is one form of low-pressure warning: a mechanical arm drops into sight when pressure sinks below roughly 60 psi, and an automatic version lifts back out of view once pressure climbs above that point.

   Source: Michigan CDL Manual — Section 5.1.11: Low Air Pressure Warning