Indian School Bus Route Safety Reauthorization Act of 2003

Indian School Bus Route Safety Reauthorization Act of 2003 - Makes funds appropriated from the Highway Trust Fund (other than the Mass Transit Account) available for each fiscal year to States that have within their boundaries all or a part of an Indian reservation having a land area of ten million acres or more. Makes counties eligible to apply to a State for all or a portion of such funds for maintenance of public roads that are within the county that: (1) provide access to the Indian reservation; (2) are used by a school bus to transport children to or from a school or Head start program; and (3) are maintained by the county in which the public road is located. Provides that such funding shall supplement, and not supplant, any obligation of funds by the Bureau of Indian Affairs for road maintenance programs on Indian reservations, and any funding provided by a State to a county for road maintenance programs in the county.