[pierreh]

In reply to Darth-Apple's note: "I'd be interested in reading about your thoughts on SC4's subway system.": as I said earlier, I don't want to repeat here the entire lengthy 'subway rant' that I once posted in the previous version of this CJ on Simmania. However, I'll put here some essential points.

It seems (from ancient posts in Simtrop and SC4D forums) that the Maxis developers didn't have enough time to produce a better subway implementation than what we have in the game. Whether this is accurate or not, the implementation has, imho, the following shortcomings:

1. It is essentially a 'flat' implementation, that is, there is a single underground level for all subway tunnels. This means that intersecting tunnels cross each other 'at grade'. This, in turn, means that the intersection of tracks is the same as that of intersecting GLR tracks with a 'grand union' layout at the intersection, allowing to go to 3 directions (straight, left and right). Then, when we see this in the underground view:



The tracks in the tunnel have a layout identical to those of a GLR intersection with a 'grand union':



This, of course, is never implemented in the tunnel of subway networks in RL, because of the obvious problems of security and the reduction in speed, obligation to stop at signals before the intersection, etc.

In RL, when 2 lines intersect, they do this a different levels, that is, one of the lines passes underneath the other. Here is an example extracted from the track map of the Paris metro:



The blue line (Line 2) crosses the brown line (Line 11) at the station Belleville. The map shows that the blue line is on the upper level, and the brown line passes underneath it at the lower level. Each line has its own set of platforms,

The ESURE project, which is currently being discussed in Brian's Transit Mania CJ, was started to overcome this 'one-level' limitation. Unfortunately it wasn't developed sufficiently to allow a wide-scale usage. I found extremely few situations in my cities where I could implement it in a 'natural' way.


2. The 'stations' in the Maxis implementation are represented by the 'subway square' visible in the subway view in the game. There is no notion of actual platforms. I use that square as intersection between lines (limited to 2 lines). The same 'grand union' effect as shown above exists in the subway square, but I like to think that it is not trains that go from one line to the other one, but subway users that change trains. Here is a typical intersection 'under' a RTMT bus+subway combo station placed on a road (surface level view and subway level view):



The fact that it is not possible to bring more than 2 lines into a subway square limits considerably the possible layout of subway tracks - if one wants to remain
as realistic as the game allows.


Fortunately, there is a feature in RTMT that can be used to overcome that limitation, where feasible: the RTMT Avenue Subway+Bus combo stations cover a 2x2 area, in other words, 4 tiles. All those 4 tiles are part of the 'subway station', even when only one of them contains the subway square. One can take advatage of this to bring more than 2 lines into the station, and to place double tunnels between stations on avenues on very busy lines. Here is an example with double tunnels in one of the cities in the cluster:




(The query sign for the station contains 'STREET', this is a bug that will be fixed in the official RTMT Version 4; the station is placed on an avenue).


I can't resist the pleasure of showing one of my favorite subway pictures: the intersection of 3 lines of the Paris metro, near the station Opera. The picture is taken on the line at the lowest level; the second line crosses above it on the middle level, and the undergirders of the bridge carrying the 3rd line can be seen on top of the picture:



This intersection was built 'in advance' when the first of the lines was constructed; the two other lines came later. This piece of engineering work is now over a century old.


I hope that I have answered the query properly. Since subways are a favorite subject of mine, if there are more questions I'll be happy to reply.