From: lip@s1.gov (Loren I. Petrich)
Subject: Re: Alliance for a Paving Moratorium (Alert)
Organization: LLNL
Date: Tue, 5 Jan 1993 19:45:34 GMT

In article <1530@dosbears> dosbears!mikel@pyramid.com writes:
>In article <1993Jan5.004707.15935@pbhya.PacBell.COM> whheydt@PacBell.COM (Wilson Heydt) writes:
: In article <1993Jan4.194523.20123@ntmtv> adrian@ntmtv.UUCP (Adrian Brandt) writes:
: >In article <1992Dec30.164607.5327@pbhya.PacBell.COM>, whheydt@pbhya.PacBell.COM (Wilson Heydt) writes:
: >|> In article <1992Dec30.002600.12884@pbhye.PacBell.COM> mjvande@PacBell.COM (Mike Vandeman) writes:

: >Time for some BOTECs (Back Of The Envelope Calculations).

: >At best, a freeway lane can handle 1,800 cars per hour, an average of a
: >car every 2 seconds.  Using a typical 1.1 people per car average, that
: >gives a lane a people throughput of 1,980 (which I'll call 2,000 just to
: >be generous).

: >Now, a railroad track and its associated signalling typically allow for
: >a maximum of a train every 2 to 5 minutes, depending on the system.  For
: >CalTrain, a locally well-known heavy rail system, I'll use the 5 minute
: >figure with 8 car trains.  Each car has seating for 148 people.  So an
: >8 car train seats 1,184 people.  Trains every 5 minutes means 12 trains
: >per hour which means seating for 14,208 people per hour per track.

>If CalTrain upsets you, try BART.  2.5 minutes headways thru SF, 3.0
>minute headways in the rest of the system.  Claiming that CalTrain
>can do 5.0 headways is being generous, in my opinion.  BART not only
>can achieve those headways, they do -- right under a big 10 lane
>freeway.  CalTrain is not restricted by technological constraints.

>And, CalTrain's 8 * 148 is probably close to BART's seating capacity
>(not to mention standing room.)

	Actually, the maximum BART train length is 10 cars. And each
car can seat 64 or 68 people. This leads to a maximum of 640 people.
The BART cars are also roomy enough to allow for a lot of standees.
How many? Probably 40/car before the crowding gets too bad. I wonder
if the BART folx have ever done their version of a car-stuffing
contest -- see how many people can fit inside.

	It would be interesting to see how CalTrain would fare here,
since its aisles are rather narrow and its upper floors are open with
only a railing to keep people from falling through.

	Headways? The minimum is 3.5 minutes, and that only for peak
service along the San Francisco segment. The other outlying lines have
to be content for 10-20 minutes. 640 people every 10 minutes is nearly
4000/hr, and that amount of people per 3.5 minutes is 11,000 people/hr.
Adding 40 standees/car yields 18000 people/hr.

	These figures are scheduled to be improved as the BART folx
develop improved train-control systems that allow for headways as low
as 2 minutes, which is almost the original goal of 90 seconds. This
yields 19,000 people/hr at full seating or 31,000 people/hr at full
stuffing.

: The second issue is that, while you have cited *average* occupancy for
: cars, you've cited full seat occupancy for the trains.  If I took the
: daily ridership on CalTrain and divided by the number of trains--the
: figures for trains would be lower, and I assumed that every car seat
: is full (say--an average of 5 per car?) the freeway value would be
: much higher.  In such a comparison, a freeway lane would yield nearly
: 10,000 people per hour, and a 4-lane freeway would be 40,000 per
: hour--20,000 each way, while the train would fall to--perhaps--600
: per hour.  Aren't statistics fun?
>
>Just try to get more than 1.1 people/car.  Judging from some of the
>asocial people posting here, there would be bloodshed.  I think 1.5
>is probably an upper limit.
-- 
/Loren Petrich, the Master Blaster
/lip@s1.gov
Newsgroups: ba.transportation