What this permit is
It’s issued by the Washington State Department of Transportation to let carriers temporarily increase their registered gross weight.
- Used when you need to haul heavier loads than your current license allows
- Does NOT allow overweight beyond legal axle/bridge limits—only up to the vehicle’s legal capacity
Basic eligibility
To qualify, your vehicle must already be licensed to at least:
- 80,000 lbs for combinations
- 40,000 lbs for single-unit trucks
Eligible vehicles include:
- 3+ axle trucks
- Truck-tractors (including dromedary units)
- Truck-tractor with doubles
Key rules & limits
- Permit is issued only to the power unit (truck), not the trailer
- Weight increase is allowed up to legal capacity, max around 105,500 lbs depending on configuration
- You must still comply with axle spacing and tire limits
Duration
- Minimum period: 5 days
- Cannot extend beyond your vehicle’s license period
Cost
- $6.80 per day per 2,000 lbs (or fraction) of additional weight
- No prorating (you pay full increments)
Trip permits interaction
If your truck isn’t licensed at 40k/80k yet:
- You can use trip permits to temporarily reach that base weight
- Then purchase the additional tonnage permit
- But you’re limited to short durations (max ~9 days within 30 days using trip permits)
Simple example
If your truck is licensed for 80,000 lbs, but you need to haul 92,000 lbs:
- You buy a temporary additional tonnage permit for the extra 12,000 lbs
- Pay based on 2,000-lb increments for the number of days needed
When you need it
Use this permit when:
- You occasionally haul heavier loads
- You don’t want to permanently increase your registered weight
- You need flexibility for short-term jobs