Key rule (when it’s required)
You need an additional tonnage permit when:
- Your vehicle is already licensed at standard maximum weights, and
- You want to haul a load that exceeds those licensed limits.
Specifically:
- For combination vehicles (e.g., tractor-trailers): licensed up to 80,000 lbs, and you want to go above that
- For single-unit trucks with 3+ axles: licensed up to 40,000 lbs, and you want to exceed that
In these cases, a temporary additional tonnage permit is required to legally carry the heavier load
When an additional tonnage permit is required in Washington?