Rollover danger on N/W curve elevated line

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Rollover danger on N/W curve elevated line

Postby NE933 » Mon Jul 31, 2017 7:39 am

In the sharp turn in Long Island City, between Queensboro Plaza and 39th Ave., N/W trains enter slow most of the time, but then speed up while the last few cars are still on it. This morning it happened, and I was in the last car. It swayed back and forth so much that I prayed it wouldn't derail, tip over and land on the street below. I imagine that if the last car did capsize it will pull much, if not all, the other cars with it. Such an accident could kill and / or maim hundreds. Has anyone else noticed and given much attention?
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Re: Rollover danger on N/W curve elevated line

Postby Triaxle » Tue Aug 15, 2017 12:13 am

Chances of that are about zero. That line has been in service for about 100 years, with higher speeds on that curve than today. The timers do force too low a speed, and so when the train leaves the timer's block it accelerates after braking. This seems to be common, the MTA would rather grind the brakes then accelerate thousands of times per day so that a in the case where a drunk operator, complicit conductor and cover-for-mah-bro supervisors combine as in the Union Square wreck, the train will be moving too slowly for it to matter.
About half the weight of the subway car is in the truck assemblies, so the center of gravity in much lower than you'd think. That said, india gauge would be more stable. BART used that so that their trains could (theoretically) run over the Golden Gate Bridge.

You probably felt that swaying as the train was first leaning to the inside of the turn from going too slowly, then rocked on its springs as the last car cleared at normal speed, relieving the inward tilt but also creating a rocking motion.
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Re: Rollover danger on N/W curve elevated line

Postby GirlOnTheTrain » Tue Aug 15, 2017 6:12 am

Ever notice those extra rails on the elevated structure? In addition to the timers slowing things down, like mentioned above, those are also there to prevent a scenario like you described. If the train derails, it's less likely to fall off the structure.
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Re: Rollover danger on N/W curve elevated line

Postby jhdeasy » Sat Aug 19, 2017 11:03 pm

NE933 wrote:In the sharp turn in Long Island City, between Queensboro Plaza and 39th Ave., ...... Has anyone else noticed and given much attention?


As a boy living in Astoria in the 1954 thru 1976 era, who rode the BMT Astoria line on trips to/from "the city" (Manhattan), I once had similar thoughts which made me nervous, but I eventually learned enough about railroading that I was not worried about such an accident. I think the two tracks on the curve have a certain amount of super-elevation, where the outside rail of the curve is somewhat higher than the inside rail of the curve, which accounts for the leaning on the curve. I believe the engineering term may be "cant deficiency."

I also remember a friendly Conductor who invited my attention to the dis-used BMT trackways curving between the dis-used northern (original BMT) half of the Queensboro Plaza elevated station and the Astoria line. They remained in place until about 1963, when most (but not all) of that structure and the flying junctions east of the station were scrapped. I recall noticing they had a gentler curve and they were at a lower elevation than the BMT train I was currently riding on the high curve of the former IRT track. They looked to be a "friendlier" route to anyone who was nervous about the train leaning on a sharp high curve.

http://www.nycsubway.org/perl/show?75913
http://www.nycsubway.org/perl/show?113424
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Re: Rollover danger on N/W curve elevated line

Postby Head-end View » Mon Aug 21, 2017 7:49 pm

Triaxle, re: your comment about BART's gauge and running over the G.G. Bridge, what does the track gauge have to do with trains being able to run over a certain bridge or not?
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Re: Rollover danger on N/W curve elevated line

Postby ExCon90 » Tue Aug 22, 2017 2:22 pm

There was a theory at the time that a wider gauge would render the trains more resistant to being blown sideways in high winds, and the Golden Gate Bridge would be the right place to find them. Whether that much additional gauge width would make any difference I don't know. There were some positions taken by the planners that seem a little eccentric, like not having collision posts on the cars because, being computer operated, the system wouldn't have any collisions.
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Re: Rollover danger on N/W curve elevated line

Postby Head-end View » Tue Aug 22, 2017 6:37 pm

Yeah, such over-reliance on computers turned out to be a little over-optimistic, huh? Worked real well on WMATA a few years back........ I don't recall, have there been any collisions on BART? I only remember the bad fire they had in the Transbay Tube in 1979. Say what people will about NYC Subways signal system with trip arms being antiquated but it's a simple, effective technology that's worked pretty well for a hundred years. :wink:
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Re: Rollover danger on N/W curve elevated line

Postby ExCon90 » Wed Aug 23, 2017 3:05 pm

I'm not sure about collisions on BART, but not long after the line to Richmond started, a train overshot the bumping posts and protruded over the street below, recalling a couple of famous examples at LAUPT and Gare Montparnasse in Paris. I think it turned out some 98-cent part failed in service.
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Re: Rollover danger on N/W curve elevated line

Postby Head-end View » Wed Aug 23, 2017 7:16 pm

Sorry to be off-topic; I just can't stop shaking my head sadly at the ignorance of some BART planner who didn't think collision posts were needed because on a system operated entirely by computers, that "there won't be any collisions". That has to be one of the most ignorant statements ever made in the history of railroading. And I can think of two families of deceased WMATA train operators who would have no problem disproving that theory. :(
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