Colorado CDL — Air Brakes practice
Signals & Pavement Markings
How to read traffic signals, lane lines, and pavement markings — including yellow and white lines, arrows, and flashing lights.
Content reviewed against official driver handbooks · July 7, 2026
7 questions · pass with 6 correct. You get instant feedback and an explanation after every answer.
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. On large buses, at what pressure do low air pressure warning devices commonly activate?
Correct answer: 80 to 85 psi
It is common for large buses to have their low-pressure warning signal come on earlier, in the 80 to 85 psi range.
Source: Colorado Commercial Driver License Manual (DR 2251), Section 5.1.11 - Low Air Pressure Warning
2. What does the supply pressure gauge in the cab tell the driver?
Correct answer: How much air pressure is in the tanks
This gauge reports how much air pressure is currently stored in the tanks; a dual system has one for each half.
Source: Colorado Commercial Driver License Manual (DR 2251), Section 5.1.9 - Supply Pressure Gauges
3. When testing the low pressure warning signal, before what pressure must the warning turn on?
Correct answer: Before pressure drops below 55 psi
As you fan down the tank pressure, the low air warning must come on before pressure falls below 55 psi (or the lowest tank in a dual system).
Source: Colorado Commercial Driver License Manual (DR 2251), Section 5.3.3 - Final Air Brake Check
4. What color is the ABS malfunction lamp used to warn of a fault?
Correct answer: Yellow
Vehicles with ABS use yellow malfunction lamps to indicate that something in the anti-lock system is not working.
5. 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
An electric stop light switch that is operated by air pressure turns on the brake lights whenever you apply the air brakes.
Source: Colorado Commercial Driver License Manual (DR 2251), Section 5.1.12 - Stop Light Switch
6. Before the air pressure in the tanks falls below what level must a low air pressure warning come on?
Correct answer: 55 psi
A visible low-pressure warning is required to activate before tank pressure drops under 55 psi.
Source: Colorado Commercial Driver License Manual (DR 2251), Section 5.1.11 - Low Air Pressure Warning
7. What is a "wig wag" low air pressure warning device?
Correct answer: A mechanical arm that drops into the driver's view when pressure falls too low
The wig wag drops a mechanical arm into the driver's field of view when system pressure falls below 55 psi.
Source: Colorado Commercial Driver License Manual (DR 2251), Section 5.1.11 - Low Air Pressure Warning
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