SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/cdl-four-way-flashers-stopped

When should you use four-way flashers on a commercial vehicle?

Turn on 4-way flashers when parked at the side of the road.

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  1. Only while passing another vehicle
  2. When parked at the side of the road ✔
  3. Only at night

Why: When you pull off the road and stop, 4-way flashers warn other drivers that your truck is not moving. Do not count on taillights alone.

Huh, didn't know that: The manual says flashers at the roadside matter most at night.

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Why did the truck flash its four-ways? It just wanted to be noticed.
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References

Answer: When parked at the side of the road. When you pull off the road and stop, 4-way flashers warn other drivers that your truck is not moving. Do not count on taillights alone.

  1. California Commercial Driver Handbook (AAMVA model manual) www.dmv.ca.gov/portal/file/california-commercial-driver-handbook-pdf
    When you pull off the road and stop, be sure to turn on the 4-way emergency flashers. This is important at night.
    Checked 2026-10-10.

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