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| Re: Canarsie CBTC (96989) | |||
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Re: Canarsie CBTC |
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Posted by Stephen Bauman on Fri Jun 10 07:18:45 2005, in response to Re: Canarsie CBTC, posted by Jeff H. on Fri Jun 10 03:59:41 2005. As for the AWS, I'd debate that it "need only handle 4 tph". That may be the spec, but realistically it's a can of worms. Especially on a line like 14 St/Canarsie, where there are very few places to stash a bad order train...I think two factors dictated the AWS spec. The first factor was the line's topology itself. They simply broke the line into 4 or 5 absolute blocks, based on where the switches were. Given that a trip from 8th Ave to Canarsie takes a little less than 40 minutes and assuming that these blocks are more or less of equal length, then 10 minute headways could be maintained. The second factor was the spec that CBTC could be turned off for maintenance at night without disrupting service. Night time service levels are 3 tph, so this gives them the option to provide slightly more service. . What happens when the carborne CBTC equipment craps out (don't tell me that will never happen!)? You'll have to go OOS and move that train as if it were foreign equipment, over a considerable portion of the railroad. That's one of the reasons they have two sets of operating equipment per train. Yes, it will crap out. Yes, it will be a disaster in rush hour. However, current systems using track circuits and vital relays also crap out during rush hour with equally disaterous results. The alternative would be to make the AWS fully capable of 40 tph operation. That would make CBTC double the cost of a conventional track circuit based system and subject it to that system's maintenance cost. If CBTC is to be successful from an economic standpoint, it will not be able to rely on an AWS backup. |
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