Homer Simpson once explained that “trying is the first step toward failure.” That, in a nutshell, is the attitude regarding road construction of Washington state transportation planners using a theory called “induced demand.”
Induced demand theory says if you supply more of any product, more people will want it. Elon Musk, CEO and chief engineer of SpaceX and Tesla, recently called it “one of the most irrational theories” he has ever heard.
Transit advocates apply the theory to road construction to suggest that building more lanes will cause people to drive more, filling up any new capacity, making traffic congestion worse than before. However, they fail to apply this theory consistently, arguing that congestion will improve if people switch from cars to taking transit or riding bikes, creating more space on the road (which should just be filled up according to their theory).
Using induced demand as an excuse to stop highway expansion would also imply we should never build another hospital because it would just fill up with sick people.