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 does a supply pressure gauge tell the driver?

   Correct answer: How much air pressure is in the tanks

   A supply pressure gauge shows how much air pressure is stored in the tanks. A dual system has a gauge for each half, or one gauge with two needles.

   Source: Ohio CDL Manual — Section 5: Air Brakes

2. 2. On large buses, at roughly what pressure is it common for the low-air warning to activate?

   Correct answer: Around 80 to 85 psi

   The manual notes that on large buses the low-pressure warning devices commonly signal at around 80 to 85 psi, higher than the 55 psi minimum for many vehicles.

   Source: Ohio CDL Manual — Section 5: Air Brakes

3. 3. What color is the malfunction lamp that warns of an ABS fault?

   Correct answer: Yellow

   ABS malfunction lamps are yellow. On tractors, trucks, and buses they sit on the instrument panel; if the lamp remains lit once the start-up bulb check ends, ABS may be lost at one or more wheels.

   Source: Ohio CDL Manual — Section 5: Air Brakes

4. 4. A visible low-air warning is required on air-brake vehicles. It must come on before tank pressure drops below what level?

   Correct answer: Below 55 psi

   The warning you can see must activate before pressure in the tanks falls under 55 psi, usually as a red light and often a buzzer as well.

   Source: Ohio CDL Manual — Section 5: Air Brakes

5. 5. 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

   Trailers carry their yellow ABS malfunction lamp on the left side, either at the front or the rear corner.

   Source: Ohio CDL Manual — Section 5: Air Brakes

6. 6. How does a "wig wag" low-air warning device let the driver know pressure is low?

   Correct answer: It drops a mechanical arm into view when pressure falls below about 60 psi

   A wig wag drops a mechanical arm down into the driver's view when system pressure falls below about 60 psi; an automatic one rises back out of view once pressure is above 60 psi.

   Source: Ohio CDL Manual — Section 5: Air Brakes