Missouri 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.
Questions reviewed against the official Missouri driver handbook · July 7, 2026
3 questions · pass with 2 correct. You get instant feedback and an explanation after every answer.
Study questions with answers
3 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. How does the air brake system turn on your brake lights for drivers behind you?
Correct answer: An electric switch operated by air pressure lights the lamps when you brake
An air-pressure-operated electric switch turns the brake lights on whenever the air brakes are applied.
Source: Missouri Commercial Driver License Manual, Section 5 (Air Brakes) - 5.1.12 Stop Light Switch
2. What is a 'wig wag' device?
Correct answer: A mechanical arm that drops into the driver's view when pressure sinks below 55 psi
The wig wag is a mechanical arm that falls into view to warn of low air; an automatic one lifts back out of view once pressure climbs above 55 psi.
Source: Missouri Commercial Driver License Manual, Section 5 (Air Brakes) - 5.1.11 Low Air Pressure Warning
3. The low air pressure warning must come on before tank pressure falls below what level?
Correct answer: 55 psi
A visible low-pressure warning is required and must activate before pressure in the tanks drops under 55 psi.
Source: Missouri Commercial Driver License Manual, Section 5 (Air Brakes) - 5.1.11 Low Air Pressure Warning
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Every Missouri question is written from the official Missouri driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free