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SESK: Stuff Everyone Should Know · sesk.info/cdl-wet-road-reduce-speed

On a wet road, about how much does the CDL manual say to reduce speed?

Reduce speed by about one third on a wet road.

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  1. About one third ✔
  2. About one tenth
  3. No change with good tires

Why: Wet roads can double stopping distance. Slow down by about one third, for example from 55 to about 35 mph, to stop in the same distance as on a dry road.

Huh, didn't know that: On packed snow, the manual says to reduce speed by half or more.

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Why did the truck slow down in the rain? It did not want to make a splash.
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References

Answer: About one third. Wet roads can double stopping distance. Slow down by about one third, for example from 55 to about 35 mph, to stop in the same distance as on a dry road.

  1. California Commercial Driver Handbook (AAMVA model manual) www.dmv.ca.gov/portal/file/california-commercial-driver-handbook-pdf
    Reduce speed by about 1/3 (for example, slow from 55 to about 35 mph) on a wet road.
    Checked 2026-10-10.

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