State Highway Flexibility Act

State Highway Flexibility Act - Allows a state to elect not to participate in the federal-aid highway program, including any federal highway program under the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU).

Directs the Secretary of Transportation (DOT), beginning in FY2011, to carry out a direct federal-aid highway program to permit a state governor or chief executive officer, at least 90 days before the beginning of a fiscal year, to elect to: (1) waive the state's right to receive apportioned or allocated funds under the federal-aid highway program, and (2) receive instead a prorated amount of taxes appropriated to the Highway Trust Fund (other than for the Mass Transit Account) which are attributable to highway users in the state. Requires a pro rata reduction of such tax-equivalent amount in order to fund contract authority for programs of the National Highway Traffic Safety Administration (NHTSA) and the Federal Motor Carrier Safety Administration (FMCSA).

Requires the state governor or chief executive officer making an election to: (1) agree to maintain the Interstate System in accordance with its current Interstate System program; (2) submit a plan describing the purposes, projects, and uses to which such amounts will be put and the federal-aid highway programmatic requirements the state elects to continue; and (3) agree to obligate program amounts exclusively for projects that would be eligible for surface transportation program funding.

Directs the Secretary to carry out a similar alternative funding program for public transportation programs.