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SESK: Stuff Everyone Should Know · sesk.info/cdl-stopping-distance-parts

What are the three parts of total stopping distance?

Total stopping distance is perception plus reaction plus braking distance.

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  1. Perception, reaction, braking ✔
  2. Speed, weight, traction
  3. Signal, steering, stopping

Why: Perception distance is how far you travel while your brain recognizes a hazard. Reaction distance is how far you go before your foot hits the brake. Braking distance is how far you roll while braking.

Huh, didn't know that: Average driver reaction time is about three quarters of a second to one second.

The dad joke
Why do truck drivers think in three parts? Because stopping is a three-step program.
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References

Answer: Perception, reaction, braking. Perception distance is how far you travel while your brain recognizes a hazard. Reaction distance is how far you go before your foot hits the brake. Braking distance is how far you roll while braking.

  1. California Commercial Driver Handbook (AAMVA model manual) www.dmv.ca.gov/portal/file/california-commercial-driver-handbook-pdf
    Perception Distance + Reaction Distance + Braking Distance = Total Stopping Distance
    Checked 2026-10-10.

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