International Registration Plan (IRP)
An agreement that provides for the apportioned registration of commercial
motor vehicles based on the total miles traveled in each jurisdiction. The IRP
has emerged as the proration agreement mandated by the federal government under
the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991. All U.S. states
except Alaska and Hawaii were required to become a member of the IRP by September
30, 1996, or forfeit their right to assess vehicle registration fees for interstate
motor carriers registered in other states.