The Chief Economist of the Dept. of Transportation explains how infastructure funding works. He's being very nice and polite about it but, the only reasonable conclusion that can be made is that the Obama economic recovery plan is a likely waste of limited taxpayer dollars that could be better used elsewhere.
Welcome to the Fast Lane: The Official Blog of the U.S. Secretary of Transportation: Chief Economist Jack Wells: Transportation Spending, An Inefficient Way to Create Short-Term Jobs
I read somewhere else the suggestion that perhaps we should invest in the military versus infrastructure. We're far more likely to need an expanded and better equipped military than we are more roads given the state of the world today. And spending there would have the same trickle down effect as any other public spending like for infrastructure.