Tribal Transportation Program Improvement Act of 2003

Tribal Transportation Program Improvement Act of 2003 - Amends the Transportation Equity Act for the 21st Century to authorize appropriations for Indian reservation roads under the Federal Lands Highways Program through FY 2009.

Requires the Secretary to establish a Federal lands highway program demonstration project for Indian reservation roads and highway bridges located on Indian reservations.

Declares that an Indian tribe or tribal organization eligible to participate in an Indian reservation road program shall be eligible to receive advance construction funds for for projects on the program system.

Prohibits the deduction from any funds available for tribal transportation purposes of any related Bureau of Indian Affairs administrative expenses.

Establishes in the Office of the Secretary of Transportation a Deputy Assistant Secretary for Tribal Governmental Affairs.

Requires the Secretary of Transportation and the Secretary of the Interior to establish a Joint Indian Reservation Roads Coordinating Committee.

Requires that a tribal scenic byways component be carried out within the national scenic byways program.

Requires the Secretary to carry out a program to provide to eligible Indian tribes competitive grants for use in establishing tribal transportation safety programs.

Directs the Secretary of Transportation to issue grants to Indian tribes to establish rural transit programs on reservations or other land under tribal jurisdiction.