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Re: TA is obsessed with CBTC, and ''New'' tech for no reason.

Posted by Stephen Bauman on Fri Feb 29 12:56:06 2008, in response to Re: TA is obsessed with CBTC, and ''New'' tech for no reason., posted by North-Easten T/O on Fri Feb 29 07:40:25 2008.

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You want to know why the TA is spending money on the CBTC system, ask the Federal Government. They told the TA awhile ago that they will not pay money toes upgrading the older Signal system any more,

Phase 4 of the CBTC project - search for the guilty. They've progressed from Phase 3 (panic).

The Feds are not paying anything for the Canarsie CBTC project.

CBTC is working right for the most part, it's not running the right way because someone who order the R143's did not order enought cars to do that they had intended to do with it. If they would have order about 100 more cars then CBTC would have been %100 working right now, But instead it's about %75 of what they wanted it to be.

CBTC's principal weakness over a wayside-based system is the requirement that all rolling stock must be CBTC-equippped in order for the system to function. Otherwise, it reverts back to its Auxilliary Wayside System (AWS). This is not a problem for new transit lines or for those with no connectivity with other lines. Its implementation is definitely a problem for systems like New York whose lines are characterized by a branch/trunk topology.

if your in a CBTC train you can run 100ft behind the train in front of you.

Current equipment is designed to have a maximum stopping distance of 275 feet (up from 250 feet for the pre-WWII fleet). If one adds a safety margin of 35%, this comes to 372 feet. This is the minimum safe distance between trains to guarantee that a follower will not rear-end its leader, should the leader decide to derail. The only way to shorten this distance is to improve emergency braking rates.

CBTC equipped rolling stock has the same emergency braking rate as the non-CBTC equipped rolling stock. The notion that CBTC will permit safe operation with 100 foot spacing between trains is a complete fiction.

This raises the question as to what is the spacing between trains. A train traveling at 30 mph will cover 4050 feet in 90 seconds. If that train is 600 feet long, the distance between leader and follower will be 3450 feet with 40 tph service levels. 30 tph service levels mean a 4800 foot distance between trains. Higher operating speeds mean even greater distance between trains. Clearly, the capability of operating trains 100 or 400 feet apart will never be required.

The follower will get closer to its leader, if the follower's speed is greater than its leader's. This occurs in normal operation when the leader is stopping in a station and the follower is approaching it. The follower will not get closer than 1500 feet to its leader, assuming: service acceleration and braking rates; a 30 second dwell time in the station for the leader and a 90 second headway(40 tph).

I have come into station while the other train is moving out but still have a part of the back in so many times I can't any more.

Happened all the time, when the Flushing Line operated at 36 tph; the Queens Blvd Line operated at 34 tph and the Lex Express operated at 32 tph. They have signals and trippers within stations to allow the follower to approach the leader within the station at reduced speed.

The Canarsie is operating at only 17 tph. Something is wrong, if the follower can get that close to its leader with those service levels.

Trains do run faster in CBTC then when they are in BY-Pass,

That's hardly surprising because by-pass limits maximum speed. The end-to-end running times for the A/B's was 35 minutes. Today it's 37+ minutes.

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