Minnesota 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
5 questions · pass with 4 correct. You get instant feedback and an explanation after every answer.
Study questions with answers
5 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 an air brake system turn on the brake lights to warn drivers behind you?
Correct answer: An electric switch operated by air pressure closes when you brake
An electric stop light switch that is operated by air pressure closes when you apply the brakes, lighting the brake lamps.
Source: Minnesota Commercial Driver's License Manual, Section 5.1.12 - Stop Light Switch
2. What is the 'wig wag' low-air warning device?
Correct answer: A mechanical arm that drops into view when air pressure gets low
A wig wag is a mechanical arm that drops down into the driver's view when system pressure falls below about 55 psi.
Source: Minnesota Commercial Driver's License Manual, Section 5.1.11 - Low Air Pressure Warning
3. What does the supply pressure gauge tell the driver?
Correct answer: How much pressure is currently in the air tanks
The supply pressure gauge shows how much air pressure is currently stored in the tanks.
Source: Minnesota Commercial Driver's License Manual, Section 5.1.9 - Supply Pressure Gauges
4. A visible low-air-pressure warning must come on before tank pressure falls below what level?
Correct answer: 55 psi
On vehicles with air brakes, a warning you can see is required to activate before pressure drops under 55 psi.
Source: Minnesota Commercial Driver's License Manual, Section 5.1.11 - Low Air Pressure Warning
5. Where is the ABS malfunction lamp located on a truck tractor or bus?
Correct answer: On the instrument panel in the cab
Tractors, trucks, and buses show the yellow ABS malfunction lamp on the instrument panel; trailers carry theirs on the left side.
Source: Minnesota Commercial Driver's License Manual, Section 5.1.16 - Antilock Braking Systems (ABS)
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Every Minnesota question is written from the official Minnesota 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