To amend the Motor Carrier Safety Improvement Act of 1999 to provide clarification regarding the applicability of exemptions relating to the transportation of agricultural commodities and farm supplies, and for other purposes.

Amends the Motor Carrier Safety Improvement Act of 1999 to revise exemptions from federal maximum driving and on-duty time motor carrier regulations for drivers transporting agricultural commodities and farm supplies during planting and harvest periods.

Extends the exemptions to drivers transporting agricultural farm supplies: (1) from a wholesale or retail distribution point of the farm supplies to a farm or other location where such supplies are intended to be used within a 100 air-mile radius from the distribution point, or (2) from a wholesale distribution point of the farm supplies to a retail distribution point of the farm supplies within a 100 air-mile radius from the wholesale distribution point.