The passageway as built is much taller than 7'6", and the floor is roughly at the same level as the Great Hall and the platforms. "Shortening" the height of that passageway means that passengers would have to go up a ramp and then back down again, which compromises the whole design of the station.

I think the passageway height needs to stay at the same elevation it is now, roughly 16'. You also need several feet of clearance beneath that for safety if you ever want to electrify the lines with modern AC technology. Low clearance at overpasses is the main reason why Metra Electric still runs 1500v DC where you only need a few inches of clearance for insulators.

There's another concern about using the bilevels at the through-platforms. For efficient through-running, you want to clear the platforms quickly. Bilevels will dump tons of people onto what will probably be narrow platforms, and then they need to walk down the platform to a vertical access point (stair/escalator). Since there is no mezzanine, these access points will be far apart. All this stuff works fine at the existing terminals, but when you need to bring in a new train every 5 minutes on the same track, you need to design everything differently.

If you think 5 minutes is unrealistic for Metra, note that even SEPTA sometimes runs 5-minute headways on each track in the Philly tunnel. I'm all for identifying cheaper ways to build the damn thing, but we need to design it for 60 years of growth, electrification, and potential regional rail like an RER or S-Bahn.

http://farm7.staticflickr.com/6046/6...166b75cf_z.jpg

I'm not sure what a thru-way rail line at the western part of the station would achieve. You would need some way to have passengers board and get to the station level. Given the current architecture, you'd have to have ramps going from the Great Hall passenger walkway down to the newly recessed platform level. The incline itself would need hundreds of feet to get to the platform level.

Here is an interesting idea that this person did as his thesis for Union Station.
http://www.coroflot.com/rikakooy/The...-Union-Station. I like the way that he opened up the floor plan, and has a grand staircase that lets you look toward the Great Hall. However, I think this design suffers from not enough bathroom space, as well as not a large enough seating area for Amtrak.

I was wondering if it is possible to create an Amtrak level underneath the concourse level, so that Metra riders and seating is at the concourse level, and Amtrak has the level below. This level would have an enlarged seating and security level. HSR would have new rails that would be underneath this level. So, the Amtrak level has access to go down the HSR platforms, and access to go up to the concourse level. Regular Amtrak trains would be accessed at the concourse level. I am concerned that such a layout may have issues with a fire evacuation. I have started to make drawings on this layout based on the thesis statement project. If anyone is interested, I'll try to post them.

Why would you need ramps? You'd have a combination of escalators, stairs, and elevators to go from concourse level to the new platforms.

To be honest, I think we should follow the Paris model, and any new through-platforms should be used for Metra service while Amtrak service continues to terminate. Shifting Metra to through trains will clear up virtually all the "capacity" problems of Union Station (the small concourse is a different matter).

As a start, join the BNSF and Milwaukee District together, so that one BNSF train would run to Elgin and the next to Fox Lake. Right away, you've cleared up at least half the platforms at Union.

Well, I guess it depends on the arrangement. I'd prefer a waiting area with gates, instead of everyone mobbing the trackside corridor through one doorway. Unions single biggest problem is cross circulation. The traditional multi level designs of waiting and platform areas needs to change in modern stations to a single floor layout. No one likes going up and down escalators with luggage. There is ADA issues, ramp space issues, elevator location issues, vehicle and heavy equipment issues with dropping the waiting room below track levels. You should only have to descend from street level to basement to board trains, and this can easily be done.

This is a pretty exciting discussion ... I can't believe the Canal rebuild was not more widely known (by me and I suppose most people) until now. It seems there is so much potential and I hope some productive use is found for every cubic yard of space beneath street level, whether rail, roadway, bus, service drive, or ped concourse related. I really hope CDOT (and every other involved entity like Amtrak) is being creative and aggressive about it.

It seems to me from diagrams that the canal viaduct is actually only half the width of Canal for most of its length, except for the block between Adams and Jackson right in front of Union Station.

Right. Short of putting all Amtrak trains on the two river tracks, the only way to keep everything flat for Amtrak is to terminate Amtrak at Union. Deeper platforms should be for Metra, just like they are at Gare du Nord.

This, of course, is exactly what Thomas Rodd created at Chicago Union Station, until Amtrak closed the taxi drives after 9/11. You walked on one level from taxi through Great Hall to ticket window to concourse to train.

Orulz, what diagrams are you looking at? The old descriptions of the Canal viaduct construction make it sound like a full-width viaduct, and that's certainly my memory at places like Cabrini where you can see underneath.

http://i39.tinypic.com/okxvrs.png
Google Street View

Interestingly, they mention having 40 feet clear between the columns, to allow construction of a "subway" at some time in the future.

The diagram posted by ardecila in this post earlier in this thread. The dashed line seems to indicate the extent of the viaduct.

Plus if you look at the pavement on Canal Street north of Van Buren, the expansion joints are only half the width of the street. Between Van Buren and Harrison, the viaduct was probably already torn down and rebuilt once when Congress Parkway was punched through the old Post Office building, so who knows what it looks like under there. South of Harrison, I agree that it seems like a full-width viaduct, but that segment has little or no relevance to Union Station.

I'm not sure exactly. Images of Tracks 1 and 2 show a poured-concrete wall along the west side of the train yard. This wall runs down the middle of Canal Street. If there were open space behind it, then one would expect to see a wall built of columns with infill panels between each one. The poured-concrete wall, on the other hand, looks like the type used as a retaining wall around the city, which would indicate that there is soil behind the wall.

Mr. D, recall that 'subway' once referred to an underground pedestrian walkway (and still does in England). Station planners probably anticipated the need to connect to the Metropolitan West Side L station that used to be where the parking garage is now, so the aforementioned subway is probably the parking garage passageway. That passageway appears to be behind the same concrete wall I mentioned above, with some windows cut out of it.

A 40' span would only take it out to half the width of Canal Street, which you yourself said is 80'.

None of this proves anything, of course. I'll be thrilled if there is a ton of unused open space underneath Canal, because it will make expansion much, much easier. It's entirely possible that it exists and we've just never heard about it - the three streetcar tunnels are documented but virtually nobody knows about them, or speaks about them if they do. It was a little weird when I saw the Wacker Drive website include a construction photo from the Washington tunnel - like I was seeing into the warehouse from Raiders of the Lost Ark or something.

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source

Remember that the future construction of shallow streetcar subways under various central area streets was anticipated at the time.

From "The Chicago Union Station, Its Design and Construction," Journal of the Western Society of Engineers, Sept. 1922:

"The substructure of all viaducts consists of a series of concrete cylinder piers, two under each column bent, which piers are spaced 40' center to center across the street, thus permitting the construction of subways between these piers at any future time. The piers are bridged by massive concrete girders on which the three columns carring the superstructure are placed, one at the center of the street and one at each curb line. The piers vary from 4' to 7' in diameter and are carried down to hardpan at –55 to –60."

Okay... from the lion's mouth.

I remember coming in on the BNSF that I thought there was extra space to the west of track 2 as the train was pulling into the station. I thought there was room for another track or 2.


Expansion for what? Do we have not have enough tracks at Union? If this space were used for additional track space, would a potential CTA subway be underneath these tracks?

I guess that settles it.

Is "serious" condition worse or better than "poor"?

Also, when CDOT says they want to "rehabilitate" the viaduct, that implies something less than the complete teardown/rebuild that they did for Wacker, so any sort of reconfiguration or widening is therefore completley out of the question.

In short, no, there aren't enough platforms, especially on the south side. FRA regs require brake tests, engine cycling, and all sorts of other things that severely limit how fast a terminal track can be turned over.

The solution is to build through-platforms so that Metra and/or Amtrak trains can continue through the station after a few minutes discharging passengers.

You can't just connect the north side tracks to the south side ones because it would split the concourse in half, requiring a new concourse to be built above or below the existing one. Plus, the tracks don't line up, so you'd have a weird and substandard kinked platform.

That leaves a subway under Canal as the most logical option. With 100' of right-of-way, we could build 4 tracks and two 16' wide island platforms.

Even if you exclude and then include the sidewalks there, I'm not sure I understand how you go from 50' to double that width and then back to 50'. For example, the sidewalks between Adams and Jackson really don't look very wide, not as much as 25' each.

Thanks, ardecila. Another puzzle in the CDOT description is the part between Van Buren and Harrison, where Canal was depressed significantly for the construction of Congress. Surely that isn't on structure the entire distance.

16' seems a bit on the narrow side for a platform that, with through running in force, might potentially have to handle all the loading and unloading passengers for two trains simultaneously (ie four train loads worth of passengers.)

Given the 10'6" wide loading gauge, I suppose platforms would begin approximately 5'6" from track center. With 15' track spacing (and 7'6" between track center and walls) which is perfectly adequate for a station area, that leaves room for two 24' platforms.

I'm using Riko's diagrams, assuming his diagrams are to scale. The distance between 222 Riverside and the Great Hall building is 60'. Part of track 1 and 2 are already under Canal.

Current Metra platforms are approximately 15' in width, going on a rough estimation on the diagram. The actual width may be smaller.

Through routing really doesn't fix the issue of destination traffic. Most traffic occurs at rush hour going into or out of Chicago. Usually after those trains are finished unloading, they will head into the yard and wait until the next use at rush hour. In the current configuration, the trains are already at the places where they are needed the most. Also your idea of creating new platform under Canal would completely disconnect those platforms from the rest of the station.

Before we add any more tracks, I think the idea of traffic management needs to be tackled.

Oh, yes, you're right. I forgot that loading gauge is not the same as car width, and car width is the most important metric in station design (assuming your platforms are straight).