
Using Countdown Clock Data to Understand the New York City Subway - lil_tee
https://toddwschneider.com/posts/nyc-subway-data-analysis/
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anthonybsd
>The L train is also the only line that uses modern >communications-based
train control (CBTC), which allows >trains to operate in a more automated
fashion.

It's not "more automated fashion", it's fully automated, LIDAR and all - they
are fully autonomous. L trains have operators because of unions throwing a fit
and most of the times they sit there twiddling their thumbs.

~~~
RossM
I feel it's worth reminding that there's a difference between autonomous
trains, driverless trains and unattended trains. The L train is considered
Grade of Automation 2 - it starts and stops itself, though it has someone in
the driver's seat who controls the doors and gives control to the ATO system.
Driverless (GoA3) trains move that role to a train attendant who controls the
doors from within the train. Unattended (GoA4) trains function without needing
an on-board operator at all.

The driver probably is just sitting with a hand near the emergency stop button
most of the time, but they're still required to pay attention. I imagine it's
harder work now that they don't have to necessarily concentrate to operate the
train.

I live in London, where a lot of tube lines are already (or soon to be) GoA2,
with the introduction of a part-GoA2 mainline service this year (Thameslink).
I don't think we'll see a GoA 4 tube for many years; aside from the obvious
union rows, you've got safety concerns (primarily platform-edge-doors, which
can't be retrofitted to cramped stations), and there's mixed public opinion on
the idea of being stuck on a broken down train in a tunnel without on-train
staff. Then again, people don't seem to acknowledge that the airport terminal
transfers are unattended GoA4.

~~~
onion2k
Does the DLR count as a GoA3 train? There isn't a driver sitting at the front.

~~~
tialaramex
Yes, each DLR train has a Passenger Service Agent, who is fully trained in the
safe driving of a DLR train by a human, but during normal operation they're
walking around in the train, closing the doors when it's ready to leave, and
so on.

The PSA will drive the first train on each route every morning, since unlike
the train's automation their human eyesight allows them to detect some very
dramatic mistakes, for example if maintenance engineers left a metal trolley
full of equipment halfway across the line, the train can't see that but the
PSA can hit the "Stop" override. Normally they don't drive, allowing
passengers to sit at the very front of the train, like on a roller-coaster,
the manual controls are under a lockable panel.

The train also has a "full" manual mode in which the PSA is able to explicitly
drive it wherever they want, rather than just stopping unexpectedly if they
see a problem, but in this mode the train deliberately cannot reach its normal
speed, because humans have poor reactions and so it would be too dangerous
without the machine supervising.

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exegete
The author does briefly mention this, but the countdown clocks are not every
accurate. I often see a wait time of "3 min" and then it's there in the next
10 seconds. Or you can see the opposite where it just hangs on "3 min" for a
minute or two and was really 5 minutes away. In reality it should just report
at its accuracy, e.g., "<5 min" "5-10 min", "10-15 min", etc.

PS, why do people stick their necks over the tracks to look if a train is
coming?

~~~
graedus
> PS, why do people stick their necks over the tracks to look if a train is
> coming?

You can often see further down the tunnel from an angle close to the tracks
than you can standing behind the yellow strip. If someone ahead of you on the
platform is already doing this, then they're probably blocking your view down
the tunnel, so you have to lean to see past them. It seems pretty silly, but
sometimes it's useful, for example, in determining whether the express or
local will come first, and you can then switch platforms at the last minute if
it makes sense for you.

If countdown timers were reliable and accurate, fewer people would feel
compelled to lean out.

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erikig
Kudos to MTA NYC - the raw data to perform analysis is available here:
[http://web.mta.info/developers/MTA-Subway-Time-historical-
da...](http://web.mta.info/developers/MTA-Subway-Time-historical-data.html)

The details on how the countdown clocks work is available here:
[https://www.amny.com/transit/subway-countdown-clock-
complain...](https://www.amny.com/transit/subway-countdown-clock-
complaints-1.15351692)

GTFS Format: [https://developers.google.com/transit/gtfs-
realtime/](https://developers.google.com/transit/gtfs-realtime/)

~~~
1wheel
That feed archive haven't been updated in years; you have to scrape and save
the feed yourself or scrounge together different sources to look back in time.

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Alex3917
I notice the numbered trains are all coming out ahead of the lettered trains.
Is this taking into account the bug in the MTA data where the countdown clocks
for the lettered trains weren't accurate at the terminal stations until a week
or so ago?

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turdnagel
Bless Todd W. Schneider and his in depth mathematical analyses of travel times
in NYC. See also his epic Uber/Taxi post:
[http://toddwschneider.com/posts/analyzing-1-1-billion-nyc-
ta...](http://toddwschneider.com/posts/analyzing-1-1-billion-nyc-taxi-and-
uber-trips-with-a-vengeance/#update-2017)

~~~
macintux
I found it interesting to contemplate how much harder it would be for someone
to do this level of analysis and draw conclusions from it if they weren't
physically proximate.

I love remote work, and I hope to sustain it for the rest of my career, but
there is something to be said for direct exposure to the systems you study.

(It also makes me appreciate all the more how hard it must be for
archaeologists et al to glean details of the past from fragmentary evidence of
a world long gone.)

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hendersoon
This is interesting analysis, but it's based on NYC MTA countdown clock data
which is just rampantly inaccurate on lines other than the L. It is regularly,
customarily, up to 4 minutes off in either direction, in my experience.

Since trains are supposed to be spaced out 4-5 min or so, that means the clock
is only really useful to tell if there's a huge delay.

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puzzle
He's completely right that the data is messy and sometimes makes no sense at
all. Even a passenger waiting for a train, if paying attention, will notice
trains appear, disappear and "jump around" on the countdown clocks.

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xhrpost
Moving due to the L tunnel shutdown next year, I've been asking if any other
train comes nearly as often (I rarely wait more than 5 minutes). This is a
very timely list, thanks!

