13. The air leakage rate for a combination vehicle (engine off, brakes on) should not be more than _ psi per minute.
Detailed Explanation
The correct answer is "4". This question tests controlled braking, heat management, and maintaining steering control. Because the prompt uses negative wording, identify the normally correct safety rules first, then select the exception.
Correct Answer: 4
Why This Matters on the CDL Test
This question belongs in your brake safety review. Pay close attention to pressure limits, inspection steps, stopping distance, and warning signs because brake-system mistakes are a common reason CDL applicants miss endorsement questions.
How to Remember It
Say the rule in your own words, then explain why the wrong answers are unsafe or incomplete. That habit makes similar Combination Vehicles questions easier when the exam changes the wording.
Answer Review
Choose "4" because this answer matches the safe CDL action for brake system safety. On the knowledge test, the safest answer is usually the one that protects space, control, visibility, legal compliance, or inspection accuracy before the vehicle is put at risk.
Why the other answers are weaker
- 2"2" does not best answer this brake system safety question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
- 1"1" does not best answer this brake system safety question. When you see a similar option on the CDL permit test, compare it against the exact safety rule and choose the answer that prevents the most immediate risk.
Test-Day Checklist
- Read the question once for the topic, then read it again for the exact CDL action being tested in Combination Vehicles.
- Eliminate answers that sound convenient but skip an inspection, warning sign, or safety step.
- Say the correct rule out loud before moving on so you can recognize it when the exam changes the wording.
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26. The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than psi per minute. a. 2 b. 3 C, 4
28. You are driving a combination vehicle when the trailer breaks away, pulling apart both air lines. You would expect the trailer brakes to come on and:
12. If the service air line comes apart while you are driving a combination vehicle but the emergency line stays together, what will happen right away?
18. You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the:
22. Air Lines on a combination vehicle are often colored to keep them from getting mixed up. The emergency line is _; the service line is _
Keep Studying Combination Vehicles
Question pages help you review one rule at a time. To build test-day speed, move back into the full Combination Vehicles practice test and answer a mixed set without looking at the explanation first.
State CDL Practice Paths
After you understand this answer, use a state practice path to connect the federal CDL rule with the DMV test pages drivers search for most.