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I forgot about the Clinton Street Subway. That would be a great additional as well, by tying in the two big suburban Metra stations directly to the CTA. Additionally, we can then split the blue line into two separate lines, the Forest Park and O'Hare lines that both terminate in the new big underground loop. This will allow the CTA to focus higher frequency train service on the busier O'Hare branch without having to do so on the Forest Park branch, or having the trains turn around at UIC-Halsted or the IMD.