In a previous article, I explained that the federal gasoline tax was a very crude way to fund highways, because there is only a tenuous link between gasoline consumption and highway usage. I followed up with an article explaining that once you add in state and local taxes on gasoline, you're already talking over 20 percent of the price of a gallon at the pump, and furthermore the proposed hike of 25 cents per gallon would push the tax on gasoline above the limit appropriate for the "social cost of carbon" as estimated by the EPA.