The problem with local input, and for that matter even the traffic engineer's input, is basic lack of thought about it. For example, almost nobody knows about

The problem with local input, and for that matter even the traffic engineer's input, is basic lack of thought about it. For example, almost nobody knows about Braess' paradox, where adding roads and cause more traffic. This is not induced demand, it's simply worse traffic for the same quantity of traffic through expanded routes. And there are tons of examples of getting rid of highways where the traffic just disappears, and everybody is happier. Or, locally, people are advocating against a small commuter rail project, in economic grounds, while the same people are advocating for spending 10x on highway projects that carry about the same number of people. Blame the politicians, but they are mo stupider than organized groups.