Each state legislature has passed regulations that set the legal vehicle sizes and weights for their particular jurisdiction. The limitations cover the legal limits allowed for width, height, length, and weight for various vehicles and/or trailer configurations. The regulations also address the limitations for vehicles traveling on interstate or designated highways within the state and/or other state or supplemental highways.

The Federal Highway Administration (FHWA) is responsible for setting size limits that must be allowed on the National Network and weight limits for the Interstate Highway System and Defense highways.

The federal bridge formula is used for roads that are designated as being part of the National Network, and while most states use the federal bridge formula for all roads in their state, some have a separate state formula they use for other state or county roads.