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SimSig goes abroad for a fun special controlling what some say is the busiest interlocking in the world - a stunning piece of trackwork that forms a major junction on Chicago's elevated metro system, called Tower 18.
This simulation is free even though there has been a lot of research and development gone in to it. This is because there are still a lot of unknowns and some (hopefully educated) guesswork involved. However, we have used whatever information could be gleaned in order to make it as realistic as we could. References to "probably" in the text below relate to unknowns.
The Chicago metro system is formed of several lines, named by colours. The lines we're interested in are the Green, Orange, Pink, Brown, and - in rush hours - the Purple Line. These converge on the downtown Chicago area and are elevated at this point above street level. Trains travel on steelworks about 20 feet above the roadway, and passengers climb staircases from streetlevel to the stations above in order to board trains.
The Loop itself is a double track rectangle around the downtown area. Two opposite corners are just 90 degree bends with a 10mph speed restriction (denoted by the "10"s on the display). The third corner is a double track triangle junction (or wye/Y) where trains can either continue on the loop or head towards Midway airport in the suburbs. The fourth corner is the aforementioned piece of trackwork that consists of two three-way junctions, a two-way junction, and a quadruple diamond in the middle.
Along plain line the track is divided into short block sections of 30-90 feet long in the Loop area, though longer out in the suburbs. There are no signals for the plain line: instead the driver (engineer) has an in-cab signalling system of some sort. However, block markers can be seen beside the track as yellow plates with a line name and a distance marker. "LP1 45" is loop track 1, 4500 feet from a known location. "SSL2_3" probably means "South Loop", track 2, 300 feet from a known location. The loop distances increment all the way around the loop.
The trains themselves are formed of fairly short carriages of about 45 feet in length (compared to 60-70 feet for main line railways typically) in order to get around the very sharp bends. Trains are usually formed of 4 or 8 cars.
Though most of the signalling throughout the entire metro area was redone within the last ten years, somewhat surprisingly a lot of the signalling/dispatching is done locally, i.e. not centralised. We have two areas of control in this simulation, Tower 18 and Tower 12. We don't know much about Tower 12 but there is a reasonable amount of information about Tower 18 (see links).
The operator in Tower 18 sits at a push-button console looking out directly over the diamonds. From this perch above the tracks he or she can directly see trains approaching from the two loop directions. By looking left and right, to the rear, he can see trains approaching from those lines too. The front of each train has a colour-coded set of lights which indicate the route the train is taking. The operator can then use his skill and judgement to route trains over the junction appropriately.
In SimSig we do not have the luxury of 3d views (and operating a push button console on a 2d computer monitor just doesn't work) so instead we see the traditional SimSig display with headcodes approaching. These headcodes (in the supplied timetable) have a letter prefix and a three digit running number suffix. The letter prefixes used are as follows:
The display also shows which lines run on which tracks and in what direction around the loop. We can see that the Brown line trains enter from Merchandise Mart, go around the loop anti clockwise (counter clockwise), then exit back at Merchandise Mart again. The Green line enters from Roosevelt, goes around the bottom of the loop, then exits at Clinton - and vice versa. There are thus a large number of conflicting moves at both towers but these cannot be avoided in order to provide good service to both loop sections in both directions. That said, the upper loop section (or south-western section) sees fewer trains than the lower (north-eastern section).
Routesetting is carried out in a similar manner to the traditional N-X way (which Tower 18 also seems to do, albeit with push buttons). Left click on the entry signal, then left click on the exit signal or the opposing (wrong direction) signal.
Note that there are some double reds. What seems to happen is that while there are no overlaps as such, signals do require a clear block beyond a red signal to get a yellow aspect reading towards the red, or the speed is reduced sufficiently to enter the next block at a low speed. As long as there is a route set you do not need to do anything for a double red.
Green route set lines are used instead of the white traditionally used in British signalling systems. Green is the colour used by American dispatching displays - though it would appear Tower 18 bucks the trend by using white LEDs instead!
Adjacent to Merchandise Mart and Clinton there are river bridges which open to let river traffic pass. Though the controlled signals have been simulated, the bridges themselves have not. It is not known how these operate.
A four-hour timetable is supplied. Several lines advertise a specific timed timetable (eg 09:10, 09:16, 09:22 etc) whereas others vary (eg between 9am and 10am trains run every 4-7 minutes). With the supplied timetable we have tried to provide an average interval service mingled with the specific timed timetable. There may well be clashes at Tower 18 especially: just try to work around them the best you can. We also welcome new timetables in our Downloads area!
Have fun. Again, we've done our best for this free simulation, but are aware there may be several bits "not quite right". Any information you can supply to make this more realistic would be appreciated. Just enjoy it and try not to send too many trains around the loop more than once!
Some interesting links for you. These all point to external sites so we cannot guarantee they are still valid or appropriate.
|Welcome to Chicago "L".org, the internet's largest resource for information on Chicago's rapid transit system! Feel free to browse the site and offer comments here.|
|CTA Towers & Junctions - Sept/Oct 2010 - Connections - Chicago Transit Authority|
|CTA Ride the Rails: Brown Line (YouTube time lapse cab ride)|
|CTA Ride the Rails: Orange Line (YouTube time lapse cab ride)|
|CTA Ride the Rails: Green Line (YouTube time lapse cab ride)|
|CTA Ride the Rails: Pink Line (YouTube time lapse cab ride)|
|CTA - Pink Line Part 1 (Rear view, real time)|
|Ride the Rails: Real time videos|
This is an Adobe Acrobat PDF file. If you don't have Adobe Acrobat Reader installed on your computer you can get a free download of the latest version from the Adobe website . When checked during January 2015, it had reached v11 and the download size was just under 50MB.
Released 8th January 2015
Released 25th December 2014
Last edited by GeoffM on 15/09/2016 at 03:00