Maximum Legal Weight Allowed
Legal Weight Maximums
|Two Tire Axle||500 pounds per inch width,* except**|
|Steer Axle||600 pounds per inch width|
|Gross Vehicle Weight||105,500 pounds|
*As marked by the manufacturer on the sidewall. Metric conversion to inches: divide metric size by 25.4 (i.e., 285 ÷ 25.4 = 11.22 in).
**Fixed steer axles, driver operated, equipped with single tires are limited to 600 pounds per inch width. Other than the steer axle, axles carrying more than 10,000 pounds and equipped with single tires are limited to 500 pounds per inch width. For other exceptions, refer to RCW 46.44.042 Maximum Gross Weights – Axle and Tire Factors
Maximum Permit Weight Allowed
Permits may be issued if the load cannot reasonably be reduced and if WSDOT determines that the structures and roads over which the load is to travel can sustain the weight without undue stress.
Permits for heavy loads are not to exceed weight limits as follows:
- 600 pounds per inch of tire width;
- 22,000 pounds on a single axle;
- 43,000 pounds on a tandem axle.
The weight allowed on any series of axles can be computed by the following formula:
|Distance in Feet Between First and Last Axles in the Group||Weight Allowed
|7 feet to less than 10 feet, multiply||(Feet) x 6,500 pounds|
|10 feet to less than 30 feet||(Feet plus 20) x 2,200 pounds|
|30 feet or greater||(Feet plus 40) x 1,600 pounds|
• Bridge restrictions may limit single axle capacities to 21,500 pounds or less on selected highways.
The lesser of any of these calculations will govern the capacity of any series of axles.
The weight on a single axle (at 600 pounds per inch tire width) may be up to 45,000 pounds if the equipment being moved has single pneumatic tires having a rim width of 20 inches or more and rim diameter of 24 inches or more, or dual pneumatic tires having a rim width of 16 inches or more and rim diameter of 24 inches or more. Specially designed vehicles manufactured and certified for special permits prior to July 1, 1975, may also be allowed.
Over Axle Permit (Overweight)
An over axle permit is for a load that falls within the legal gross weight, but axle(s) is over the legal weight limit. Over axle weight on an axle would be weight exceeding 20,000 pounds on a single axle and 34,000 pounds on a set of tandems. Tridem weight would depend on the measurement between the three axles. After determining the distance, check the vehicle weight table to see what the legal capacity would be. The price of the permit is calculated with the amount of weight over the legal axle weight and the number of miles to be traveled.
Heavy Haul Corridor-Overweight Sealed Container
The department may issue special permits to vehicles operating in the heavy haul industrial corridor at the Port of Tacoma to carry weight in excess of weight limitations established in RCW 46.44.041. However, the excess weight on a single axle (22,000), tandem axle (43,000), or any axle group must not exceed that allowed by RCW 46.44.091(1) and (2), weight per tire must not exceed 600 pounds per inch width of tire, and gross vehicle weight must not exceed 105,500 lbs. An overweight sealed container used in international trade, including its contents, is considered non divisible when transported within a heavy haul industrial corridor, such as SR 509 between milepost .25 in the vicinity of East “D” Street and milepost 3.88 in the vicinity of Taylor Way.