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Old Posted Feb 18, 2014, 6:56 PM
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Wizened Variations Wizened Variations is offline
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Quote:
Originally Posted by electricron View Post
London, Moscow, and Seoul have rivers bisecting them less than a mile wide. The Bay Area has San Francisco Bay bisecting it, which can be 4 (Bay Bridge) to 7 (San Mateo Bridge) miles wide and 33 miles long (Bay Bridge to Milpitas). Putting those distances into prospective, 33 miles in the London area stretches from M25 west of the city to M25 east of the city as a bird flies along the Thames. The English Channel between Dover and Calais is just 25 miles wide. Yes, just the south Bay is longer than the crossing.
The Bay stretches further north, and just by itself (uninhabitable swamp and bay) is larger in area than central London.
I don't think the Bay Area is geographically the same as the three cities you mentioned, and I highly doubt circular transit patterns will work. The Bay Area is set up for linear transit lines, not just by the Bay coastline but by the surrounding hills/mountains as well.
Ignore the landscape and distances involved at your peril. I don't think you would advocate building a circular tunnel under the channel, so why are you suggesting building a circular transit lines around the south Bay?
The issue is frequency of travel and switching from feeder loops.

Both should occur, but the most important is the Bay Loop.

The time taken to travel under the Bay is rather short- from the West Oakland Station to the Embarcadero Station takes 7 minutes.

http://www.bart.gov/schedules/byline...ate=02/18/2014

Each tunnel should be close together.

The model I am using was posted by Itsmotorsport, 021614, #1017 on this blog.

What the Bay Loop would do:

A) Directly connect 13 stations.
B) Directly connect (with the critical Alernate Cut-Offz) 5 feeder lines if one includes Caltrain.
C) Provide a very well served 6 station core (6 stations) directly in SF, from which rider synergies would radically increase. These six stations would be no more than 1 km or so from the one of the tube lines.
D) Within 1 transfer (a quick Alternate Cut-off ride) an additional 4 or more stations- say 10 minutes out from either Civic Center or Central/Subway forms a dense station net.
E) The same situation would exist on the East Side, with a tight cluster of stations (proposed Alameda, Lakeshore/Grand, and existing McArthur (need to complete the loop her) 19th,12, and West Oakland Stations.
F) Eliminate delays caused by feed lines.
G) Provide backup for if one Tube needs to be repaired.
H) Provide very short headways for trains.

You did make me think, though, at a far cheaper solution

I would interested if something like this just used the existing tunnel. The same tight loop could be made by collapsing the loop, something like a figure "8" with a line segment expanding the center cross over. This certainly would be straight forward on the Bay side, but on the Bay side a circular connector would have to made further south, built in less developed land. Ball Park Station would then lie on a feed line, i.e., would then be 1 transfer away from Oakland.

The geometry still works and with 2000 person capacity trains at 3 minute headways we are still taking about 40,000 rider per hour capacity in each direction.

Again the key to the Oakland/SF end of the Bay is a very frequency fast loop with easy, quick transfers. And, this does not have to be done with two tunnels (although 160,000 riders per hour ranks with the worlds best.)

Thanks for getting me on the 'right track.'

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The south loop is rather nebulous, because, as you point out, much of the Bay patterns are linear. In addition, we have variables like integrating the Caltrain train which has standard track gauge (BART does not) and a loop of additional track layer to go around the south end of the Bay. Based on your input, I think any second loop would have to involve two transfers in the loop (at each end of a segment on the Caltrain line) and would not provide a good rider increase per cost.

Incidentally, as has been discussed by OhioGuy, this blog #1029, others have suggested extending Caltrain and a new (standard gauged) tunnel under the Bay and forming a 2nd loop formed by extending Caltrain through Jack Lon and Hayward and possibly completing the loop either across the Bay or just to to the south (the cross bay would be new) and the most of the rest mixed use).

IMO there is little reason to do this short term. I think that the key to this possible two transfer loop would be the speed of BART from Hayward around the south side of the Bay. A possible improvement on the BART portion would be 4 track passing stations from Fremont south through San Jose to Santa Clara.

The keys to the South Bay transit, IMO, boil down to the speed and frequency of the Caltrain, and, the speed on BART south of Fremont.
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Good read on relationship between increasing number of freeway lanes and traffic

http://www.vtpi.org/gentraf.pdf

Last edited by Wizened Variations; Feb 18, 2014 at 7:26 PM.
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