BART Train length

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inetpub

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Jul 2, 2000, 3:00:00 AM7/2/00
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"david ross" <dami...@catlover.com> wrote:
> While reading the BART short range transit plan, I
> came across something that doesn't make any sense.
> Why does the state say that the minimum train
> length for BART must be 3 cars? Why can't it be 1
> or 2 cars? Is there an operational reason for
> this or is this just another stupid state law?

It can't be one car for obvious reasons... a BART
train must have cars with operational controls on
both the lead and end cars because terminating
stations do not have looping turnarounds.

As to why it must be 3 cars instead of 2 cars is an
interesting question. I am speculating here, but I
assume that it is because BART platforms are super
long... around 710 feet from end to end. It is hard
enough for a person to run from the end of the
station to attempt to catch a three-car train. It
would be even harder to catch a two-car train.

Thus, I believe the three-car requirement is in
place in order to reduce the dwell time at stations.
Otherwise, the operator would have to wait until all
patrons have caught up to the train.

-----------------------------------------------------------

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Silas Warner

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Jul 2, 2000, 3:00:00 AM7/2/00
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david ross wrote:
>
> While reading the BART short range transit plan, I came across something
> that doesn't make any sense. Why does the state say that the minimum train
> length for BART must be 3 cars? Why can't it be 1 or 2 cars? Is there an
> operational reason for this or is this just another stupid state law?

Well, it's not exactly stupid but it's obsolete. Originally BART had
pointy-ended A cars and cabless B cars. The ends of BART trains had
to be A cars and the middles B cars. Because there were only a few
A cars to a bunch of B cars, the state originally set up a provision
that every train actually have a B car -- thus no two-car trains.
Now BART also has flat-ended C cars that could in theory be used for
2-car trains or coupled into longer sets.

Silas Warner

david ross

unread,
Jul 3, 2000, 3:00:00 AM7/3/00
to
While reading the BART short range transit plan, I came across something
that doesn't make any sense. Why does the state say that the minimum train
length for BART must be 3 cars? Why can't it be 1 or 2 cars? Is there an
operational reason for this or is this just another stupid state law?

--
David
http://damiross.go.cc/
Bay Area Nautrists
The Naturist Society
Nude is not Lewd

RicSilver

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Jul 3, 2000, 3:00:00 AM7/3/00
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inetpub wrote:

DR> While reading the BART short range transit plan, I came across something


that doesn't make any sense. Why does the state say that the minimum train
length for BART must be 3 cars? Why can't it be 1
or 2 cars? Is there an operational reason for this or is this just another
stupid state law?

There is no such law. It may be a regulation or rule that BART has established
itself.

In>It can't be one car for obvious reasons... a BART train must have cars with


operational controls on both the lead and end cars because terminating stations
do not have looping turnarounds.

This is similar to Caltrain or most other rail operations.

In>As to why it must be 3 cars instead of 2 cars is an interesting question. I


am speculating here, but I assume that it is because BART platforms are super
long... around 710 feet from end to end. It is hard
enough for a person to run from the end of the station to attempt to catch a
three-car train. It would be even harder to catch a two-car train. Thus, I
believe the three-car requirement is in place in order to reduce the dwell time
at stations. Otherwise, the operator would have to wait until all
patrons have caught up to the train.


Nice try but... That would be fine, except that short BART train alway stop
so that the train is centered at the middle of the platform. Additionally the
sign will blink "5 car train" if the train is less than 8 cars, giving those
few people who stand at the veryend of the platform to reposition themselves.

Try again...


Richard Silver
650-368-7112

david ross

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Jul 3, 2000, 3:00:00 AM7/3/00
to
>
> DR> While reading the BART short range transit plan, I came across
something
> that doesn't make any sense. Why does the state say that the minimum train
> length for BART must be 3 cars? Why can't it be 1
> or 2 cars? Is there an operational reason for this or is this just
another
> stupid state law?
>
> There is no such law. It may be a regulation or rule that BART has
established
> itself.
Ric - there IS a law according to the SRTP. The Public Utilities Commission
requires a minimum of a 3 car length according to the SRTP

Kevin Standlee

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Jul 3, 2000, 3:00:00 AM7/3/00
to
david ross wrote:
>
> While reading the BART short range transit plan, I came across something
> that doesn't make any sense. Why does the state say that the minimum train
> length for BART must be 3 cars? Why can't it be 1 or 2 cars? Is there an
> operational reason for this or is this just another stupid state law?

The train length selector switch in the cab has a "2" setting, as I
recall. (It's my long-legged tall blonde wife who gets offered the
BART cab rides by sweet-talking the drivers, not me, so I'm speaking
from just peeking through the doors.) Therefore, the 3-car minimum
length is probably just an operational requirement -- that is, by
internal rules, they won't run a train shorter than that.

It's been a while since I last rode BART, but as I recall, they
generally don't run anything shorter than a four-car train.

And that reminds me: BARTs plans for the Millbrae extension assumed
that every rider on every Caltrain arriving at Millbrae would transfer
to BART. How do they expect to carry that many passengers? The
Caltrain train would carry more people than the BART train could hold!

--
------------------------------------------------------
Kevin Standlee | Fast / Accurate / Cheap
<standle...@menlolog.com | Pick Any Two
------------------------------------------------------

inetpub

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Jul 3, 2000, 3:00:00 AM7/3/00
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rics...@aol.com (RicSilver) wrote:

In> As to why it must be 3 cars instead of 2 cars is
> an interesting question. I am speculating here, but
> I assume that it is because BART platforms are super
> long... around 710 feet from end to end. It is hard
> enough for a person to run from the end of the
> station to attempt to catch a three-car train. It
> would be even harder to catch a two-car train. Thus,
> I believe the three-car requirement is in place in
> order to reduce the dwell time at stations.
> Otherwise, the operator would have to wait until all
> patrons have caught up to the train.

RS> Nice try but... That would be fine, except that


> short BART train alway stop so that the train is
> centered at the middle of the platform.
> Additionally the sign will blink "5 car train" if
> the train is less than 8 cars, giving those few
> people who stand at the veryend of the platform to
> reposition themselves. Try again...

My point was that even with a three-car train, you
need to walk about 1/3 the distance of the platform.
With a two-car train, you need to walk about 40% the
distance of the platform. If dwell time is a
concern, a three-car train will board in less time
than a two-car train.

Jim Middleton

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Jul 3, 2000, 3:00:00 AM7/3/00
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BART's minimum train length is indeed 3 cars as ordered by the
California PUC. This is due to concerns about the BART train control
system's ability to detect a train that is drawing no power.

Unlike normal railroad and light rail signal systems which use from 6 to
10 volts rail-to-rail differential to detect the presence of a train in
a particular
section of track, BART uses 0.1 volt to detect trains. The low voltage
impairs the ability of the train control system to see trains. The
system
operates by shorting the circuit between the two rails via the wheels
and
axles, which conduct electric current. Rust, oil, smoggy condensate,
and
other "pollution" on the head of the rail reduces conductivity, hence,
train
detection.

In testing prior to opening of the system, the PUC and BART
determined that the reliability of the train detection when a 1-car
train
was shut down was about 99.5 percent. This means that 1 in 200 trains
would not be detected, and the train control system could command a
following train to operate up to maximum track speed into a collision
with the dead train, an unacceptable event. The reliability of
detection of a 2-car train was determined to be somewhere above 99.9%,
but still below the railroad industry standard. At 3-car length, the
performance of the train detection system was up to the standards
accepted in the railroad industry.

Therein lies the rationale for the 3-car minimum. You may ask why the
concern for detection of a dead train. Several different
trouble-shooting scenarios require a complete shut down of a train to
reset various systems. With a short train (1 or 2 cars), the train
would be unacceptably vulnerable to loss of detection during this
shutdown, which lasts several minutes.

BART is working on development of its own "Communications Based Train
Control" system along the lines of Muni's Seltrak system. This might be
the key to running shorter trains.

inetpub wrote:

--
Jim Middleton
webm...@lightrail.com
http://www.lightrail.com
http://www.lightrail.net

David Barts

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Jul 3, 2000, 3:00:00 AM7/3/00
to
Jim Middleton wrote:
> [...]

> Unlike normal railroad and light rail signal systems which use from 6 to
> 10 volts rail-to-rail differential to detect the presence of a train in
> a particular
> section of track, BART uses 0.1 volt to detect trains. The low voltage
> impairs the ability of the train control system to see trains. The
> system
> operates by shorting the circuit between the two rails via the wheels
> and
> axles, which conduct electric current. Rust, oil, smoggy condensate,
> and
> other "pollution" on the head of the rail reduces conductivity, hence,
> train
> detection.

Why on earth did they choose such an apparently ridiculously small
voltage? Yet another instance of "if it uses some existing technology
that's Not Invented Here, it won't be Space Age BART Technology"?

--
David W. Barts (dav...@scn.org) / http://www.scn.org/~davidb
Oakland, CA, USA

edef...@my-deja.com

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Jul 4, 2000, 3:00:00 AM7/4/00
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In article <j5T75.29362$_b3.7...@newsread1.prod.itd.earthlink.net>,

"david ross" <dami...@yahoo.com> wrote:
> While reading the BART short range transit plan, I came across
something
> that doesn't make any sense. Why does the state say that the minimum
train
> length for BART must be 3 cars? Why can't it be 1 or 2 cars? Is
there an
> operational reason for this or is this just another stupid state law?


When BART began operations in the 70's, there was a problem "losing
trains," ie the computer system not being able to locate all trains.
BART had to resort to a manual system and a at least a 3-car length in
order to get the state to approve transbay service.

--
Edward M. DeFranco


Sent via Deja.com http://www.deja.com/
Before you buy.

Anonymous

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Jul 4, 2000, 3:00:00 AM7/4/00
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Since posting the previous message, I received a message from a
source who wishes to remain anonymous. I am forwarding it almost
complete, as my source requested, to ba.transportation. Please
do not reply to me personally: this material comes from another
source.

Silas Warner
------------------------------------------------------------------

I could post myself, but lets say I don't like
"public" commenting, nudge-nudge, wink-wink.

If you don't want to hear from me, just reply and let
me know.

Regarding the train length... Trains can run in
"automatic" mode with as few as 2 cars, to a number
limited only by the resistance of the train line. 20
car trains have been run out of service after hours
(actually, only once I know of).

In general, there must be a "control" car (A car, or
closed up C car) in the front, and one in the back.
There cars close the "loop" of train line, required
for automatic operations (there are exception for
emergency use, but I will skip that for now).

The 2 cars trains were discontinued for safety
reasons. First, if one car's brakes fail, or have to
be cut out, that leaves only 1 car with working
brakes. This would be 50% braking power, which was
decided was not sufficient enough to carry passengers.
Generally, 66% brakes are needed to run with
passengers, 50% for out of service trains. For
example, if a six car train has 2 cars without working
brakes (we are talking friction brakes here), then it
can run (at reduced speed), but if a 3rd car goes, its
out of service, if a forth goes, it gets parked
somewhere until either a car is fixed, or more cars
are connected.

The other reason for no two car trains is that the
possibility of two cars having a failure at the same
time, or shortly after one another, is not THAT small.
If this were to happen, the train would be, well, not
easy to stop except by collision or detail (there are
some other options, but you get the idea). That
never occurred, but the risk numbers were
unacceptable. By changing the rule to 3 cars, with at
least 50% brakes to move at all, they reduced the
likelihood of catastrophic failure to a level where it
will (odds willing) never happen.

If you set the train length dial to "2" in the front
cab, the train will not run in automatic (anymore).
If you set the rear cab to "2", even if the front cab
is not, the train will run, but the doors will not
work in automatic mode.

As another side note, you can set the train line to
whatever you want, regardless of the actually train
length. The train does not know how long it is on its
own (that may change someday). You may notice that
sometimes a 9 car train is sent out in what is usually
a 10 car trains slot, but still stops at the 10 car
marker (end of the platform). The Train Operator is
running with the dial set to 10, so they do not have
to suffer the abuse from the passengers walking back
past the cab to get onto the train (you can imagine).
Strictly speaking, this is against the rules, but I
was present when a female T/O was actually hit
(slapped) in the face by a customer upset about
running a short train (as if the T/O has any control
over that whatsoever. Central and the yard
supervisors decide this, and it usually is because we
are short cars for maintenance reasons).

As long as I am yapping on and on, you may be
wondering what the train length dial is for then. It
is primarily used to set the computer as to where to
stop at the platform, and used with the number of
cut-outs to determine if the train can run, and if it
will run at full speed, reduced speed, or half-speed.
The train DOES know how many cut-outs it has
automatically.

It's the best of 1960 technology mish-mashed with
1980's technology at work for the people! Woo-Hoo!


wabi007

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Jul 8, 2000, 3:00:00 AM7/8/00
to
as a train operator I just wanted to clear this up.It is totally impossible
for the train to be 2 cars in length, the computer on board that handles all
automatic functions will not accept a length of 2 cars.Also a 2 car train
can only hold 80 or so people "Crushed" into it ...... not fun
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