State motor fuels excises continue to be the predominate source of state revenue for transportation improvement projects.  Our review shows that as of March 2014, Pennsylvania, which is the latest state to increase its motor fuels excise, has the highest gas tax rate at 40.7 cents-per-gallon; Alaska has the lowest, at 8 cents-per-gallon.  The national average state gas tax is 24 cents-per-gallon.  Fifteen states have gas tax rates under 20 cents-per-gallon.  The federal gas tax is 18.4 cents-per-gallon.  For a state-by-state comparison, click Gas Tax Rates February 2014.