So I was going to save this post for later as part of a series on Chicago transit (good stuff coming!), but I set off an enthusiastic discussion on Twitter this afternoon about the concept of using a little tunneling to through-route regional rail and high-speed trains through downtown Chicago:

.@IngthirInhacre My pet project is a tunnel from Millennium via Clark/Lake connecting to UP-N and electrifying the whole thing. So much $$$ — Sandy Johnston (@sandypsj) July 7, 2014

Click on the tweet or my feed to read the whole discussion. Since this seems to be what we Jews call in Aramaic inyana d’yoma, the matter of the day, I figured I’d do a brief bit now; maybe I’ll come back to it in more depth later.

Several urbanist/transit writers, most prominently Stephen J. Smith (now at NextCity) and Alon Levy, have been beating the drum about the massive potential of using what are currently regarded as “commuter” rail lines through city centers, effectively turning them into all-day-usable, frequent “regional rail” systems. Most of these analyses that I’ve seen have focused on East Coast cities like Philadelphia, New York, and Boston. The concept, though, has also taken root in Chicago; the Gold Line proposal has long made a compelling case for rapid-transitizing the Metra Electric District (no seriously, this is a no-brainer), and the Midwest High Speed Rail Association’s ambitious CrossRail Chicago plan combines infrastructure preparations for true HSR with through-routing of commuter trains.

CrossRail Chicago is, to me, the single most ambitious and potentially transformative transit project Chicago has seen in a long time (short of the full Transit Future slate being built, of course). But why, I ask, stop there? The CrossRail plan still relies on renovating a couple of relatively low-capacity, vulnerable pieces of infrastructure: the two-track, sharply-curved, St. Charles Air Line, and the currently mostly-unused run-through tracks at Chicago Union Station. Trains would have to make several sharp turns to transition between legacy rights-of-way that weren’t intended to work together, meaning that they’d have to travel through downtown pretty slowly–something that might impact HSR trains severely (Today, Amtrak trains coming into CUS from the Air Line back into the station–I once sat on the connection on a late-running City of New Orleans for a full hour while the Metra rush-hour trains made their exit. To be fair, that connection would be upgraded under the CrossRail plan). But the CrossRail plan would only transform two of Metra’s numerous commuter rail lines into regional rail-type operations, and there’s only so much that can be done when through-running relies on two low-speed run-through tracks. Can we aim for something more ambitious?

The stereotype of Chicago’s commuter rail system is that it predominantly shares its tracks with heavy freight traffic. That’s certainly true of a couple of the busiest lines–UP-W and BNSF–but several Metra lines actually see little or no freight traffic. (For those not familiar with the Chicago rail network, CMAP’s map of freight trains per day on various lines is an invaluable resource.) Metra Electric trains share a ROW but not tracks with freights; meanwhile, freight is for all intents and purposes nonexistent on the UP-N and UP-NW corridors, nearly so on the Rock Island District, and at manageable levels on the Milwaukee District lines and the SouthWest Service corridor. That’s a lot of potential for rapid-transitization, probably more than the CrossRail proposal can handle. So how might we handle a full rapid transitization of the Chicago commuter rail network?

Here’s one idea:

What you’re looking at is a system of tunnels connecting the Metra Electric District, Rock Island District, and all of the North Side lines (UP-W, NW, and N, MD-W and N, NCS), with the focal point being an underground superstation under the CTA hub along Lake Street between Clark and Wells. Tunnels would curve north and west from the existing Millennium Station to run under Lake Street, passing under the existing CTA subways to a deep-level station, and reconnecting to the rail system west of the Chicago River. Meanwhile, a second set of tunnels would bypass LaSalle Street Station (or stop at new underground platforms underneath it), and run under LaSalle Street until joining the east-west tunnel under Lake.

Aside from enabling high-speed through-running through the Loop, this system would mollify what has always been one of the biggest complaints about Chicago’s commuter and intercity rail stations: that they don’t connect well with the city’s transit system. A superstation running several blocks under Lake Street could connect regional and intercity trains alike, including HSR, with ALL of the L lines that run through the Loop (I couldn’t get the transit layer to display in the new Google Maps editor, but they’re all right there). And it would bring commuters into the heart of downtown, closer to the densifying (and already very dense) River North area.

Such a project would, of course, be massively expensive (not my area of expertise–Alon, if you’re reading this, want to leave some estimates in the comments?), but I’d argue it’s a much better solution for future true HSR than using the geometrically-restricted and somewhat remote Union Station. Bringing through-routed riders into Clark and Lake is also far preferable to dumping them at Union Station. It’s probably in the realm of fantasy. But sometimes it’s fun to dream.

Notes

The connection between the LaSalle tunnel and the Lake tunnel is awkward, and I’m not sure where the LaSalle platforms would go. But that’s probably deal-withable.

I’ve tried to note what I think would be realistic portal areas for these tunnels. Arguably, you could get some of them closer and save some money by taking a few buildings, but the further the portals are from the deep-level station, the less steep the grades down will be, which helps speed.

Dennis Griffith suggested re-using one of Chicago’s under-appreciated lower level streets to bring trains to River North. That’s an intriguing idea, but I’m not sure how feasible it is (trains would have to cross other lower-level streets at grade, for one thing), and I’m not sure where trains would go on the other end.