Air Brakes
This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Idaho Commercial Driver’s License Manual l. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.
Number of Question
Passing Score
7. A low air pressure warning signal should activate:
Explanation
In an air brake system, a low air pressure warning signal must come on if air pressure in the tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a wig wag.
8. A safety valve is set to open at ____ pounds per square inch (psi).
Explanation
The safety valve protects air tanks and the rest of an air brake system from accumulating too much air pressure. The safety valve is usually set to open at 150 psi.
9. The leakage rate for a triple combination vehicle with air brakes should be no more than ____ in one minute during a static leakage test.
Explanation
When performing a static leakage test on a triple combination vehicle with air brakes, the leakage rate should be no more than 5 psi in one minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.
10. What helps prevent wheel lockup when braking?
Explanation
The purpose of an Anti-Lock Braking System (ABS) is to prevent wheel lockup while brakes are being applied.
11. In a dual air brake system, air pressure should build from 85 to 100 psi within ____ seconds.
Explanation
When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.
12. When leaving your vehicle unattended:
Explanation
