From: mikel@dosbears.UUCP (Mike Lipsie)
Newsgroups: ba.transportation
Subject: Re: Alliance for a Paving Moratorium (Alert)
Date: 5 Jan 93 05:07:49 GMT
Reply-To: dosbears!mikel@pyramid.com
Organization: DOS Bears

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:
>>|> >>Actually, a light rail line can carry the equivalent of a freeway, I 
>>|> >>am told. They can reach 55 MPH or more.
>>|> >
>>|> >Actually, I believe that a heavy rail line can carry far more than any 
>>|> >freeway full of SOVs, so is in a class by itself.
>>|> 
>>|> I wouldn't be *too* sure about that....  LA (for instance) has some pretty
>>|> wide freeways...
>>
>>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.
>
>Now let's *both* look at reality.  You've assumed two things--first
>that trains *will* be run at the kind of headways you're talking
>about.  While you are (no doubt) correct that CalTrain (per your
>example) *can* run 5 minute or less headways--do they?  I seem to
>recall complaints about 2 *hour* headways at some times of the day...

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.)

>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.

--
Mike Lipsie                            584 Castro #614, San Francisco, CA 94114
dosbears!mikel@pyramid.com
mikel%dosbears.uucp@ingres.com    Running rn (for DOS) with UUPC/Extended 1.11k
Newsgroups: ba.transportation