Transit in Parks Act - Directs the Secretaries of the Interior and Transportation to establish and administer a transit in parks program to encourage and promote the development of mass transportation systems in the National Park System for improving visitor mobility and enjoyment, reducing pollution and congestion, and protecting park resources. Sets forth requirements for such program, including the development of transportation plans for units of the National Park System and the making of grants and contracts for the planning, engineering, design, and evaluation of mass transportation projects in such units and for capital projects and investment.