The Director of the Missouri Department of Transportation says the emphasis on better gas mileage has an unintended consequence: it undermines the way we pay for infrastructure. Kevin Keith says gas tax revenues are flat but the cost of building roads and bridges continues to rise. Asphalt that cost $26 a ton 20 years ago costs $60 today. Concrete has jumped from $50 a cubic yard to $150.

Keith says a gas tax big enough to solve the problem won’t work. He says it’s time to consider a sales tax on fuel.