Do states have to adopt the Federal Bridge Formula?

The Federal Government has mandated that all states must allow specific size and weight requirements in order to meet the “Federal Bridge Formula” which was issued in January 1994. Although originally setup for weight spacing on bridges, the Formula is used to determine the “minimum” requirements all states must allow on the designated highways, interstate or National Network roads in their state. But should individual states want different limits set on other state roads — that is their option. While the majority of the states have adopted the Federal formula for all roads in their state, some states have set up their own state bridge formula which allows for different (usually higher) limits on state or supplemental highways. In most cases though, they are very similar to the federal formula but never less than the Formula.