Checksum: 51098 Lines: 105 Path: utzoo!sq!msb From: msb@sq.com (Mark Brader) Date: Mon, 20-Mar-89 21:18:18 EST Message-ID: <1989Mar20.211818.27937@sq.com> Newsgroups: tor.general Subject: Re: TTC Subway fault-tolerance References: <810@mv03.ecf.toronto.edu> <446@ontenv.UUCP> Reply-To: msb@sq.com (Mark Brader) Distribution: tor Organization: SoftQuad Inc., Toronto Keywords: TTC, Subway, delay, fault,turn-around > > Although the problem was near Davisville, there was no service > > between Lawrence and Union. I know that there are gurus out there > > who will agree that there is a switch-over thing (=x=) just > > south of St. Clair Stn. The term you want is "turnback switch"; the particular layout you show is a "scissors crossing" (for obvious reasons). Actually, there *was* a scissors crossing just south of St. Clair, but it was removed two or three years ago. The original line from Union to Eglinton was more richly provided with turnback switches than the later parts of the system, and I believe the TTC observed that they weren't being used all that much and decided to save on maintenance costs by taking some of them out. It costs more to maintain switches than plain track because of uneven wear; with plain track you can grind away any irregularities, but with switches you have to keep the rail-tops level on both branches of the switch. The other turnback switches that were removed were also scissors crossings; they were just south of College and just north of King. You can see that the tunnel loses its center wall (and the ceiling becomes arched to span the extra distance) at these locations. > Wednesday's problem made it necessary to shut off power to the rails, I'm > pretty sure the power is "zoned" but likely Davisville and St. Clair > are in the same zone. There are certianly other reasons too. That's a sufficient reason all by itself, and I'm sure it is the actual reason. Eglinton station has turnback switches on *both* ends -- a scissors crossing south of the station and a center "pocket" track north of it -- but it must be in the same zone too. > A better question would be why the trains couldn't turn at Bloor > instead of Union. Apparently because Bloor is in the same zone too. This surprised me also. In fact, I was one of those affected by the problem, because I was trying to go from King to Bay stations at the time. I walked to Union and made the trip via St. George instead. While I was leaving the subway at Bloor station, I noticed that there was a train stopped at the northbound platform and its interior lights were off. So it seems there was no power on the Yonge line at Bloor either. It's possible that the accident happened very near a power zone boundary, and two adjacent zones had to be switched off. Maybe I'll ask the TTC about it. I too was surprised that they had to shut down so long a section. The following is a complete list of possible turnback switches on the subway system to the best of my recollection; however, I'm doing this from memory, and it's been some time since I've used some of the lines, especially the farther northern and eastern sections. This list is really posted only to give an idea of how they are placed; if anyone wants to correct it, please email to me and I'll post a followup. I say "possible" turnback switches because some of them may be intended for other purposes than turnbacks, and may not have the necessary signals to be used that way without special intervention. By "trailing" crossover, I mean one that the train has to reverse *before* using, i.e., as you approach it you see it cross from the left to the right track. "Leading" is the opposite. nearest station layout Finch scissors crossing Finch center track Sheppard scissors crossing York Mills scissors crossing Lawrence scissors crossing Eglinton center track Eglinton scissors crossing Davisville trailing crossover Davisville leading crossover Bloor scissors crossing Union trailing crossover Union to St.Andrew center track | Anyone know why they have Osgoode center track | two so close together? St. George scissors crossing St. Clair West center track Glencairn center track Lawrence West center track Wilson scissors crossing Kipling scissors crossing Islington scissors crossing Islington center track Jane scissors crossing Keele scissors crossing Ossington center track St. George scissors crossing Broadview center track Greenwood scissors crossing Woodbine scissors crossing Victoria Park scissors crossing Warden center track Warden scissors crossing Kennedy scissors crossing Most of the center tracks can be entered from either end, but I won't bother trying to remember which ones can't. Mark Brader "Well, I didn't completely test it, and SoftQuad Inc., Toronto of course there was a power failure the utzoo!sq!msb, msb@sq.com next day." -- Louis J. Judice