At 55 mph, brake lag adds about 32 feet to your stopping distance. Brake lag is the time it takes for the air to travel through the lines and activate the brakes after you press the pedal, which is about one-half second.
The CDL (Commercial Driver License) exam tests your knowledge of commercial driving rules, safety procedures, and vehicle operation. You must score 80% or higher to pass the written knowledge test. The exam covers general knowledge, air brakes, combination vehicles, and various endorsements.
This question is from the Class B CDL Air Brakes Test #1 section. Practice with more questions from this category to build confidence before taking the official DMV test.
Browse All Free CDL Practice Tests →