Here is a picture of the lower deck design on February 27, 2006, the earliest file save I have a record of:
Grid lines are 1' apart. This is comparable to the high-level design sketch from that earlier post.
At this point in the design process I was still getting used to the CAD tool. I hadn't started using text labels, colors, or providing any details except the outlines of the benchwork and the main track. I also hadn't done much work on staging yet.
Most of the track design at this point was nothing like the final design, but one area that was very close to final was the Union Station on the north wall:
I put a lot of thought into how many tracks Union Station should have. My concept of commuter train operations wasn't as well formulated then as it is now, per the layout concept description I recently posted, but I did know I wanted enough tracks to support heavy traffic and make operations interesting. This was a highly subjective decision -- the sort of thing about which reasonable modelers can disagree. Eventually I decided that 6 tracks would be too few but 8 just enough to give a sense of a busy Union Station.
The next challenge was fitting everything in. Each station platform had to be 10' long, per the maximum passenger train length. Granted, the maximum length for the commuter trains is only 5', but as this Union Station has a long history I couldn't seen any rationale for shortening the platforms from what would have been built in years past. (Reducing the number of tracks from years past does make sense in order to reuse the land, but reducing existing platform length would have had little benefit as the tracks would still be there.) When you then add the need for switch ladders on both sides, plus 36" minimum radius curves at each room corner, PLUS the need to have room for double track main adjacent to the station tracks, it was a struggle to fit it all in.
Fortunately, one question I'd toyed with during the concept phase was whether to have the station be stub (tracks that terminated in the station) or through (tracks that extend in both directions from the station). At that time I studied existing and past Union Stations, and noted that Kansas City had a mix of stub and through tracks, and thought that might be a neat idea. It was important to note that for the modern St Albans Union Station 3/4 of the traffic would depart in one direction -- towards the junction -- so it made sense to me that half of the 8 tracks would be stub ended, servicing only that direction. This would also make operations planning more interesting, as it introduces a new constraint regarding track assignments. Finally, from the design perspective, this meant that the switch ladder on the east side (left in the above diagram) would be significantly shorter, thus giving me enough space to fit everything in.
I've mentioned before that I love the intracate trackwork leading to congested city Union Stations -- not just Chicago but other cities as well. On the east (left) side I used curved switches to save space. On the west (right) side 3 double slips were used to help create a double crossover as the main entrance to the station. This is but a tiny fraction of what is used in Chicago, but it does give the feeling of complicated, congested trackwork that I was seeking.
This next picture focuses on the northwest corner of the lower deck (the lower right of the diagram). Although all of these tracks were redrawn at some point the basic schematic still remains in the implementation today:
The main junction between the two double-tracked lines is shown at the top. One main line is shown going diagonally from the lower left towards upper right (this is the N-S main). The other (the E-W main) may be difficult to identify because there are so many tracks in the picture. The three tracks to the far right in the picture, the ones going straight along the right wall, are the interchange tracks between the two main lines. If you follow these downward you'll see they merge into one, using curved switches in the bottom right corner, and that one track then connects them to the double main line. Although these tracks appear to be right next to the main line tracks, what the diagram doesn't show is that there is a widening elevation difference as the main line gains elevation and the interchange tracks slope downwards.
The elevation difference was because I decided early in the design process that the junction would be a bridge of one line over another, not a level crossing. This was another one of those decisions that required a lot of thought. A level crossing is certainly more interesting operationally. However, given the traffic density for these lines it seems to me that a bridge crossing would have been a requirement -- especially a century earlier when the Union Station would have hosted 40+ tracks and automatic traffic control wasn't even a concept. On the plus side, this gave me a good reason for introducing gentle grades (1% maximum) to add visual variety.
At the same time, I wanted the scene to contain evidence of there having been even MORE traffic in past years. Although both main lines are now double-tracked, the layout will have signs that more tracks were used on the main lines in years past. One example of this is the track which goes from Union Station to the E-W line. You'll see that it connects with the main, but also that two other tracks extend along the main line towards the junction. The purpose of this track is to go from Union Station to the commuter train storage and maintenance yard (on the layout peninsula). There is a dual track for a short distance which serves as a runaround track. These dual tracks are positioned as if they are on the same roadbeds that in years past hosted the 3rd and 4th track of the E-W main line -- back when traffic density justified that many main line tracks.
Perhaps the most interesting item in this diagram is that trains leaving Union Station on this side of the layout have 3 choices of direction -- one toward the E-W main line, and two toward either direction of the N-S main line. The radius for these tracks is tighter than the main line -- one of them actually is set at the 24" minimum radius for slow speed yards. All in all they succeed in providing the sense of an interesting, complex, network of track at the entrance to the Union Station.
There were a number of things that needed adjustment in this diagram, and these would be taken care of in later iterations. The biggest issue was the "S-curves". The back-to-back switches are just not realistic. There needs to be at least one car length between switches to avoid the S-curve problem.
Otherwise, referring back to the first diagram at the beginning of this post, the rest of the track shown for the lower deck would not survive future revisions. On the left side of the diagram you'll see a single track spur from the mainline. The idea here was that this spur would meander through city streets then ultimately end up on a landing along the river, going under the main line, and that the bridge over the river would be in the upper left corner. As I reworked this later I would toss out the idea of having remaining industry along the river as being both inconsistent with my vision for the city, and also a sign of trying to do too much in the space. This last point is purely subjective, but it was the conclusion I came to.
The last point I'll make regarding the lower deck is my decision to include a commuter train yard on the peninsula. Although the track for this yard would be revised, I kept the yard in that location. The question about whether a downtown yard made sense was another one of those subjective decisions. One option would have been to argue that there would be commuter train yards at the suburban ends of each line, where real estate is cheaper and where most trains would originate. This would also allow me to put some sort of interesting industry on the lower deck peninsula instead of a commuter yard. However, I eventually decided that consolidating all maintenance operations in one central location would be a money saver, and thus a likely result of the 1970s consolidation of all commuter railroads in the city, and that the real estate in question would have been available from other railroad uses that the SAMR (St Albans Municipal Railway) would have owned. In addition, the commuter yard operations are turning out to be at least as interesting as those of a freight industry, and have the benefit of being unusual for a model railroad.
So that's where the lower deck design was on February 27, 2006. At that time I'd also done some work on the upper deck, but it was not as far along:
This does roughly follow the high-level design concept for the upper level. The peninsula is used for a branch line, terminating in the railroad museum. The railroad museum concept would later evolve so that it now matches what is described in the high-level design post. There is a commuter station on the right side of this diagram -- that would remain in that location, but only after extensive modification.
There is a first attempt at a freight yard on the left wall, with part of the yard spilling over to the bottom wall. This attempt was entirely unsatisfactory and resulted in a long study of frieght yard design which I'll cover in a separate post.
As a final note in this post, you'll see there is no evidence of staging in either of these diagrams. In fact, there were staging tracks in this version of the design, but they were in separate CAD layers so are not shown. At this point they were very rudimentary. Much of the work over the next several months would be struggling to find a suitable staging approach. This will be part of the discussion in the next design post.
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