|
|
| Re: TA is obsessed with CBTC, and ''New'' tech for no reason. (579794) | |||
 |
|||
| Home > SubChat | |||
|
[ Read Responses | Post a New Response | Return to the Index ] |
|
||
|
Re: TA is obsessed with CBTC, and ''New'' tech for no reason. |
|
|
Posted by Jeff H. on Mon Mar 3 03:58:47 2008, in response to Re: TA is obsessed with CBTC, and ''New'' tech for no reason., posted by Stephen Bauman on Sun Mar 2 21:23:30 2008. Clearly, keying by and station time were not necessary for the 30, 32, 34 and 36 tph peak service levelsof the 1950's (through early 1970's). They occurred but they were an anomaly not a necessity. Your thought experiment is too long-winded for me...I would have to draw it out to follow what you are saying. I have some documents that the BOT used to lay out the IND signal system. They start with a required service level and then plot a series of time-distance-speed curves on huge pieces of graph paper, using the actual grades and acceleration and braking profiles. They reach the conclusion that station time IS necessary in many cases to reach 40 tph (90 second headways). I'm not sure why you reach a different conclusion. You may be neglecting the fact that signal system has an overlap. There are always at least two red signals in approach to the stopped train. If you assume a block length of 600', there is a red at the station entrance, a red 600' back, and a yellow 1200' back. The follower would need to be 1800' to see all greens. As for keying-by, of course that was not intended to be required to meet service under ordinary conditions. However, when there was a variation in dwell time causing bunchng (often beyond the crew's control, e.g. door holding) then keying-by allowed better recovery from the disturbance. |
|
|
|