(posted as Transport Politic comment)
Chicago was always a surface-lines town, which served it well when the region was essentially a series of factory towns orbiting around a commercial core. But travel patterns have changed; distances have increased and jobs have aggregated into centers and corridors (although not necessarily in transit-ready patterns).
Extending the principal cross-town rapid transit service (the Red Line) for “the last five miles” — it reaches the city’s north border, but stops well short of its south — should be a high priority. The largely low-income and transit-dependent far south side has lost countless heavy-industry jobs. Having gone there last weekend, it takes a double bus connection or infrequent commuter rail to get anywhere, compounding its distance from the N/NW “favored quarter.” These lines have been on transit plans for 100 years; the Orange Line “extension” proposed was even part of the original proposal but got value engineered out. (In the intervening 20 years, though, the original terminal area has declined economically, and I’m not sure whether it can really come back. The Yellow Line extension is interesting and restores access to a major job center, but pretty small in the grand scheme.)
Given the distances involved (12-16 mi. as the crow flies from downtown), there’s no way for surface transit to serve the same need. That said, there’s no local match money available for anything, anyways.
The Circle Line looks interesting on a map, but it’s an expensive solution in search of a problem. It serves a corridor of middling job/population density and limited growth potential, and offers minimal rider time savings. Other proposals to enhance downtown distribution, or improve crosstown buses, would offer better time savings and TOD potential.
Oh, and BRT? Impossible, since IDOT jealously guards its sacred freeway lanes, and Morgan Stanley is holding our parking meters hostage until our great-grandchildren come around.
(And an addendum on the Circle Line: a finding from a thorough calculation of its merits by Ritesh Warade finds that “the majority of the transit accessibility to households impacts of the Circle Line project have already been achieved after implementation of the Pink Line project… travel time reductions are not sufficient for the Circle Line project to have substantial accessibility impacts above and beyond those of the Pink Line project.” The marginal increase in transit riders’ accessibility to jobs that the Circle Line would achieve is 0.2%.)