washington does have all kind of vehicle laws. http://www.wsp.wa.gov/traveler/passequip.htm
All states have laws about it, most are about the same with some differences, here is washingtons.
Fender Flares & Anti-Spray Devices
Required - All vehicles, trailers, and semi-trailers must be equipped with fenders, covers, flaps, or splash aprons adequate for minimizing the spray or splash of water and mud to the rear if the vehicle. All such devices shall be as wide as the tires behind which they are mounted, and extend down to at least the center of the axle. (See required equipment for exceptions)
Are not included in the total maximum width of 8'6" for motor vehicle.
See Projections and RCW 46.37.500
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Height Requirements
Minimum Height - No part of the vehicle may be lower than the lowermost portion of the rim of any wheel in contact with the roadway. RCW 46.61.680
Maximum Heights - *Bumper (4.5" min. width)
GVWR 7501 and up = Front 28" & Rear 30"
GVWR 4501 - 7,500 = Front 27" & Rear 29"
GVWR 4500 and under = Front 24" & Rear 26"
Car = Rear 22" & Rear 22"
*(Measured from ground to the bottom of bumper) WAC 204-10-022
Body Lift - 3" maximum spacer, with body not raised more than 4" above frame when installation is complete. WAC 204-10-036
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Projections
Wheels - No vehicle may be equipped with wheel nuts, hubcaps, or wheel discs extending outside the body of the vehicle when viewed from directly above which:
Incorporate winged projections; or
Constitute a hazard to pedestrians and cyclists.
RCW 46.37.369
Body, Fender, and Bumpers - Shall be maintained without protrusions that could be hazardous to pedestrians. Bumpers shall not extend past the original bumper line. RCW 46.37.517
Safety Appliances - Such as clearance lights, flexible fender extensions, mud flaps, splash and spray inhibiting devices, and others may not extend more than 3" beyond the extreme limits of the body. RCW 46.44.010
Rear Vision Mirror - Shall not extend more than 5" beyond the extreme limits of the body. RCW 46.44.010
To the Front - Load shall not extend beyond 3' (Read for exemptions RCW 46.44.034)
To the Rear - Load shall not extend more than 15' beyond the center of the last axle. RCW 46.44.034
Outside Load Limits - No passenger type vehicle shall be operated with any of the load extending past the fender line on the left side, nor more than 6" past the fender line on the right side of the vehicle. RCW 46.44.060
