You can always put housing further from the center, but the radius of not-insane commute times is much harder to expand. Wider highways encourage further-flung

You can always put housing further from the center, but the radius of not-insane commute times is much harder to expand. Wider highways encourage further-flung suburbs, resulting in at best the same level of congestion, often more. Fortunately Chicago already has the CTA and Metra infrastructure, and we could presumably make trains longer (and run them more frequently) for a reasonable price. Though at some point you hit the limits of safe separation between trains and the inefficiencies of block signaling. CTA rail doesn't have the physical infrastructure to run express services (there are very few places where a train on a specific line can bypass another) so building more stations doesn't necessarily help you either.