How to discern the difference?
Be involved. Go to local and state meetings and ask all the tough questions.
As an example of pure pork :: In Wilmington, NC there is an intersection that has received so much repaving that it creates its own gully when it rains. That intersection is Gordon Road and Military Cutoff Road. There are layers and layers and layers of macadam to the point where when turning into or out of that intersection, one is literally driving up or down hill. Not because there is actually a rise in the terrain, but, because that road has been paved unnecessarily so many times that it has created its own elevated roadway.
President Elect Obama has PROMISED a change in infrastructure. That doesn't mean simply more of the same, but, sincere escape from stupid projects that employ a 'certain' trades-person, to rebuilding our infrastruture to manage the change this country NEEDS.