What is brake lag?
- The time from the moment you press the brake pedal to the time that the brakes start to work ✓
- The time from the moment your eyes see a hazard to the time that you decide what to do about it
- The time from the moment the brakes start to work to the time that your vehicle comes to a complete stop
- The time from the moment you recognize a hazard to the time that you press the brake pedal
Answer: A. The time from the moment you press the brake pedal to the time that the brakes start to work
Brake lag is the time from the moment you press the brake pedal to the time that the brakes start to work.
Why this is the answer
The handbook says a car's brakes begin working almost as soon as you press the pedal, but air brakes are different: there is about a 4/10-second gap between applying the brake and the brakes beginning to function. That gap is brake lag. The same passage treats braking time separately, as the time or distance the vehicle travels before it stops.
Why the other answers are wrong
- B. The time from the moment your eyes see a hazard to the time that you decide what to do about it — That describes perception time, seeing a hazard and deciding what to do, not the delay after you press the brake pedal.
- C. The time from the moment the brakes start to work to the time that your vehicle comes to a complete stop — That describes braking time, the time or distance the vehicle travels before it stops, not the delay before the brakes begin to work.
- D. The time from the moment you recognize a hazard to the time that you press the brake pedal — That covers recognition and reaction before you press the pedal, while brake lag begins only after you apply the brake.
Remember it
Keep brake lag separate from your see-think-do time: it starts only after your foot is already on the pedal.