Washington OS/OD Overview
Permit Required
Yes – all oversize or overweight loads require a permit from the Washington State Department of Transportation (WSDOT).
Legal Limits (Without Permit)
- Width: 8'6"
- Height: 14'
- Length: 75' (combo); 53' trailer allowed
- Weight: 80,000 lbs GVW (with legal axle spacing)
Permitted Load Maximums (Typical Upper Limits)
- Width: Up to 20' with escort
- Height: Over 16' requires route survey and utility coordination
- Length: Over 125' requires route review and escort
- Weight: Over 200,000 lbs with bridge/engineering analysis
Superloads require prior planning, structural review, and coordination with local jurisdictions and utilities.
Travel Hours
- Standard: ½ hour before sunrise to ½ hour after sunset
- Weekend: Travel allowed for loads under 10' wide and 105' long
- Holidays: No travel on major holidays or after 12:00 PM the previous weekday
- Night travel: Allowed for smaller loads with proper lighting and only by permit
Escort Requirements (General Guidelines)
| Dimension | Escort Requirement |
|---|---|
| Width > 12' | 1 Escort (rear on 4-lane, front on 2-lane) |
| Width > 14' | 2 Escorts (front and rear) |
| Height > 16' | High pole escort and utility clearance required |
| Length > 125' | 1 or more escorts depending on route and configuration |
Additional Notes
- All oversize loads must display “Oversize Load” signs, red/orange flags, and amber lights
- Mountain passes, ferries, and weather can impact travel—check conditions before moving
- Permits are issued through the WSDOT Electronic Permit System (WEP)
Detailed Information
PERMITS: Permits valid for three days. Must have permit prior to entering the state. Washington permits can no longer be purchased at POEs.
OPERATING TIME: One half hour before sunrise to one-half hour after sunset, All day Saturdays and Sundays. In addition, vehicle/loads not exceeding 12' wide, 14'6” high and 105' long, including legal overhangs, may run at night with proper lighting. Overweight only may travel 24/7 if they can maintain the flow of traffic.
RESTRICTED TRAVEL: Monday through Friday time/width curfew restrictions for the vicinities of Seattle Everett, Tacoma, Olympia, Vancouver and Kelso are listed on the Commuter Curfew Hours sheet which accompanies permits.
LEGAL DIMENSIONS: Width: 8'6" Height: 14' Length: 53' semi-trailer (a 56' trailer and load permit is available for legal loads) Overhang: 3' front, 15' rear from center last axle to end of load. Weight: 80,000 Gross or more, depending on number of axles and their spacings Steer – 600 lbs. per inch of width (13,200 for 11" steers) Single – 20,000 Tandem – 34,000 Tridem – 42,000 (with at least 8' of axle spacing) Divisible Loads Exceeding 80,000: You can exceed 80,000 gross without a permit on state highways and on Interstate highways as long as you are legal on all axle/group weights and you are licensed for at least the amount of your gross weight.
ROUTINE PERMIT LIMITS: Width: 16' (14' on 2-lane highways) Height: 16' Length: 125' trailer and load Note on Height Clearances: Washington state oversize permits do not guarantee height clearances on permitted routes. Weight: 99,200* (5 axles) 108,000* (6 axles) 134,000* (7 axles) *Depending on axle spacings Steer Axle – 600 pounds per inch of tire width (13,200 pounds maximum with 11 inch tires) Single – 22,000 Tandem – 43,000 Tridem – Depends on spacings (4'2" spacings get about 54,080 pounds; 4'6" spacings get about 58,500 pounds, etc.) Register for up to 105,500 pounds to permit for that much or more. Loads exceeding these dimensions or exceeding 200,000 pounds are considered as Super Loads.
ESCORTS: On Multiple Lane Highways: Width: Over 14' – 1 escort; over 20' – 2 escorts Height: Over 14'6" – 1 escort with height pole Length: Trailer length including load over 125' – 1 escort Overhang: Center last axle to end of load exceeds 1/3 of total trailer and load length – 1 escort On 2-Lane Highways: Width: Over 11' – 2 escorts; over 16' – case by case basis Height: Length: Trailer length including load over 105' – 1 escort. Overhang: rear overhang exceeds 1/3 of total trailer and load length – 1 escort. Over 14'6" – 1 escort with height pole
MISCELLANEOUS: All lift axles must be on the ground if exceeding legal axle weights. Overweight single piece loads must be reduced when possible. Loads created by means of welding, bolting, or tying will be considered to be reducible.
SIGNS, FLAGS & LIGHTS: "Oversize Load" signs are required for all oversized loads at the front of the tractor at a height of 5' from ground level (or as high as practicable on the vehicle or load if it can not accommodate the 5' height), and at the rear of the vehicle at a height of 5' to 7' from ground level (or as high as practicable on the vehicle or load if it can not accommodate the 5' to 7' height). Signs are not needed for overweight only loads. Flags must be displayed on all four corners of all overwidth loads, and at the extreme ends of all protrusions, projections, or overhangs. When night movement is allowed, loads projecting beyond the sides of the vehicle must have amber lights visible from the front and side at the outermost extremities. Rearmost edge of the projecting load must be marked with a red lamp visible from the rear and side.