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| Re: Fourth Rails and Safety (832644) | |||
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Re: Fourth Rails and Safety |
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Posted by Subterranean Railway on Sat Sep 12 17:02:17 2009, in response to Re: Fourth Rails and Safety, posted by Bill West on Sat Sep 12 15:59:02 2009. unless one is pushed, I think in falling off a 4’ high platform gravity is going to initially put you on the running rail not a center rail 5’ away.The physics of a falling human body are fairly complicated (a possible forward component of motion if the person were walking, a constantly changing moment of inertia that complicates calculations of how a person will rotate as (s)he falls, etc . . . ) Nonetheless, I think it's fairly safe to say that the further away a potential source of electrocution, the better. Especially where they are forced to be on the platform side or worse on both sides. As I said before, those are also rather dangerous. Three-track, two island platform stations are but one example in New York that comes to mind. are the top exposed 3rd rails of elevated lines much better? The lack of a top cover is actually safer, since it's harder to trip and fall while stepping over the third rail. (I've seen third rail protection boards bear workers' weights, but I know the practice is greatly frowned upon.) I wouldn’t take 12-10 as covering electrocutions because it also covers people who get back up okay. I didn't interpret it that way either. I merely used 12-10 to mean "persons on roadbed (or catwalk)" in general. My point was that 12-10s in London would be far less survivable than those in third rail-based systems, which are a fairly frequent occurrence (as I said, the vast majority of people on the roadbed, whether their presence be accidental or otherwise, slip by completely unreported.) It was the lack of qualifiers in 12-9 reports that made me think that the timing of the fall was more deadly than what they might touch in the fall. Again, it's not NYC I'm especially concerned about in that regard, it's London. You're correct in pointing out that electrocutions in NYC are fairly rare, since one'd have to be severely disoriented (or thrown hard) to touch the third rail in most cases. we didn’t worry about the degrees of exposure to people who were where they shouldn’t be, we just worried about them being there at all. I'm not talking about the safety of some high voltage switch room deep in a tunnel, but rather something that's very readily accessible. The fact is, people do frequently accidentally end up on the roadbed; not so much in the "totally enclosed station" you used in your example. To grossly hyperbolize your logic, it would be totally fine if the roadbed were ballasted with shards of broken glass and rusty nails. If people shouldn't be there at all, who cares about how safe it is? People shouldn't crash their cars, so why bother with safety features? ;-) that patent is an elaboration on basics. I didn't really care about whatever data were trying to be measured, I just liked the patent description because it described London's system of electrification fairly well. |
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