Washington Truck Mud Flap Law
Washington requires fenders, flaps, or splash aprons on every truck, trailer, and semitrailer to kill rear spray (RCW 46.37.500). There is no inch-count clearance. The flap must be as wide as the tire and drop at least to the axle center. Rigs 40-plus years old driven in fair weather are exempt. Roadside, a trooper checks that a flap exists, sits full-width, and hangs low. A short or missing flap draws a correctable equipment ticket, not an out-of-service order.
What Washington makes you run
Washington requires fenders, flaps, or splash aprons on every truck, trailer, and semitrailer to kill rear spray (RCW 46.37.500). There is no inch-count clearance. The flap must be as wide as the tire and drop at least to the axle center. Rigs 40-plus years old driven in fair weather are exempt. Roadside, a trooper checks that a flap exists, sits full-width, and hangs low. A short or missing flap draws a correctable equipment ticket, not an out-of-service order.
Coverage and clearance
- Required: Yes
- Coverage: At least as wide as the tires behind which it is mounted; dual tires must be fully covered.
- Ground clearance: No fixed inch number. The device must be as wide as the tires it is mounted behind and extend downward at least to the center of the axle (RCW 46.37.500).
- Fine: Non-criminal traffic infraction (equipment). Usually a correctable fix-it citation with a modest monetary penalty; dollar amount not fixed in statute.
Washington Mud Flap FAQ
Are mud flaps required on trucks in Washington?
How low can mud flaps hang in Washington?
What is the mud-flap fine in Washington?
Reference information for planning, not legal advice. Traffic laws change and this can be out of date, so always confirm the current statute and obey posted signs before you rely on it. Last reviewed July 2026. Source: https://app.leg.wa.gov/rcw/default.aspx?cite=46.37.500. See our Terms & Disclaimer.
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