Gasoline Savings and Speed Limit Reduction Act of 2008 - Prohibits the Secretary of Transportation from approving a federal-aid highway project for a state: (1) with a maximum speed limit in excess of 60 miles per hour on any state highway (other than a highway on the National Highway System (NHS) located outside of an urbanized area), or in excess of 65 miles per hour on any such NHS highway; and (2) that has failed to certify to the Secretary that it is enforcing such national maximum speed limits.
Prohibits the Secretary from approving a federal-aid highway project also for a state with a speed limit on any portion of a public highway within its jurisdiction which is not uniformly applicable to all types of motor vehicles using such portion of highway, if on July 1, 2008, such highway portion had a speed limit which was uniformly applicable to all types of motor vehicles using it. Allows a lower speed limit, however, for a vehicle under a special permit based on the weight or dimension of such vehicle. Makes the requirement inapplicable, also, during any time that the condition of the highway, weather, or an accident creates a temporary hazard to the safety of traffic.
Requires the Secretary to transfer up to a specified annual percentage of the aggregate amount of federal-aid highway funds to state safety projects in states that fail to enforce the national maximum speed limits.
Directs the Secretary to arrange with the Transportation Research Board of the National Academy of Sciences to study, and report to the Secretary and Congress on, the benefits of the national maximum speed limits program and the effectiveness of state enforcement of such limits.