Revises the definition of "commercial motor vehicle" with respect to federal commercial motor vehicle safety laws to include vehicles primarily engaged in the transportation of agricultural commodities or farm supplies having a gross vehicle weight or gross vehicle weight of at least the minimum weight of a commercial motor vehicle as defined by the state. (Current law applies to vehicles having a gross vehicle weight rating or gross vehicle weight of at least 10,001 pounds, whichever is greater.)
Prohibits the Secretary of Transportation from withholding commercial motor vehicle safety improvement grants from a state solely because it authorizes drivers of farm vehicles having a gross vehicle weight of between 10,000 and 26,001 pounds to operate without complying with federal commercial motor vehicle safety laws.