Across North America, there are tractor trailer size and weight regulations that must be followed. Here are some of the most common limits.

Canada

In Canada, the weight regulation is set by the provinces. Canadian Provinces generally govern semi-truck weights by specifying the number of axles, and general configuration of the truck. Then, the combination is given a maximum weight that must be followed. There is no national – level weight and dimension information that is law across the country.
There are some collaborations and some co-working that takes place across Canada. In Eastern Canada, the provinces of Newfoundland, Nova Scotia, New Brunswick and Prince Edward Island have all agreed to follow the same regulations. The rest of the country have different regulations, but have generally agreed to follow the same regulations for 8 different general vehicle combinations in a memorandum of understanding, effectively creating 8 ‘Canadian’ truck combinations. Individual provinces often set weight limits higher than these weights. See document.

United States

The United States have a federal set of standards that specify the ‘minimum maximums’ that must be allowed on federally funded highways, which include the interstates and national network of highways. On these roads, there is a standard set of rules that truck drivers can follow that are common across the country. These are the well known weight limits of:

  • Gross Weight: 80,000 lbs
  • Single Axle Weight: 20,000 lbs
  • Tandem Axle Weight: 34,000 lbs

Along with these weight limits, there are bridge laws which restrict the spacing and weight of axle groupings. The longer and the more axles a truck has, the more weight that it can carry. The bridge formula defines this relationship.

State laws

In 1992, the ISTEA act ‘froze’ the weight laws that were in place in various states. What this meant was that states that had more liberal weight laws before this act were put into place, were allowed to keep these higher weight laws in place, even on federally funded highways. States are always free to keep higher weights in place on state roads that they finance themselves.
Some of the notable states that allow higher weight limits than 80,000 lbs on federal or state roads are:

Michigan

Allows up to 11 axles on a single combination, and a theoretical maximum of 164,000 lbs gross truck. Because these limits are grandfathered, these trucks can travel on both interstate and state roads.

South Dakota

Has no gross weight limit, and no limit on the number of axles you can put on a truck, as long as the combination follows the bridge formula. 17 axle trucks carrying mainly agricultural products are common in the state, with gross weights exceeding 170,000 lbs.

New England States

In the New England states of Maine, New Hampshire, it is common to operate 6-axle semi trucks on the interstate and national network system of highways at a weights of 99,000 – 100,000 lbs. The neighboring state of Vermont also allows trucks up to 99,000 lbs as well, but these heavy trucks are not allowed to operate on the interstates and are restricted to state roads.

New York

State laws in New York allow for permitting of divisible loads. Truckers can operate a 6 axle truck at 107,000 lbs or a 7 axle truck with a gross weight of 117,000 lbs. You can also operate Long Combination Vehicles on the Thruway.