Weight Limits, Scales & Bridge Laws

Weight limits protect roads and bridges, and they protect you: an overloaded truck takes longer to stop, overheats its brakes, stresses tires and handles poorly. Getting weight right is part of the job, not just a way to avoid fines.

• Truck drivers
• Dispatchers

Federal limits on the Interstate

States set limits on other roads, and some allow more under special permits or older “grandfathered” rules. Tire and equipment ratings may be lower than the legal limit; you must stay under the lowest.

The Bridge Formula in plain words

The closer together axles are, the more they concentrate weight on a bridge. The Bridge Formula limits how much weight a group of axles can carry based on how far apart they are. That’s why sliding a trailer’s tandems or adding axles can make a heavy load legal, and why short wheelbase trucks can carry less.

Getting your weight right

1. Get the load weight from the shipper, then weigh the truck on a certified scale before you head out.
2. Check each axle group, not just the gross.
3. If drive axles are heavy, slide the fifth wheel back; if trailer axles are heavy, slide the tandems forward (and recheck).
4. Make sure slider pins are fully locked after any adjustment.
5. If you’re still over, the load must be adjusted or reduced.

Remember fuel: a full set of tanks can add hundreds of pounds to the drive and steer axles.

Weigh stations

• Pull in when the station is open and signs say trucks must enter.
• Bypass systems (transponders and apps) may give you a green light to keep going; a red light means pull in.
• Follow signs and lights on the scale; stop or roll slowly as directed.
• Weigh stations are also where many roadside inspections happen. See Roadside Inspections.

Posted bridges and roads

• Obey posted weight limits on bridges, even if your truck is legal on the highway. Some local bridges are rated for much less.
• Seasonal “frost laws” in some states lower weight limits on certain roads during spring thaw.
• Use a truck GPS that knows weight and height restrictions.

Last updated: October 1, 2026