
Marey’s Trains - inferiorhuman
https://observablehq.com/@mbostock/mareys-trains
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supernova87a
_[comments below without realizing that the post is from about a year ago, and
that the author might not be reading this...]_

That's really nice work, and I had always been curious if anyone had produced
such a chart!

I note though, looks like you're using quite an old schedule as your input
data, as the departure times of the weekday southbound trains in the plot
don't match the current morning schedule (4:55, 5:25, 6:05, 6:15, 6:35, 6:45,
6:59, 7:05, etc) which has been in place for more than 2 years. Also on the
weekends, it's missing the bullet trains (2 per day). Also for some reason if
you select the weekend, the connecting lines between data points disappear.

Aside from that, really revealing chart! Interesting to see how basically
trains can pass each other only at 2 stations: Bayshore and Lawrence. And the
"falling off a cliff" effect for trains south of San Jose / Tamien is
entertaining (though sad). One hopes that with coming electrification (will it
ever arrive?), every line will be flattened by a factor, and new lines will be
added (if what Caltrain claims about electrification turns out to be true).
Amazing how a graphic can reveal these insights better.

Is it possible to add a function to output this as PDF or save the result as
PNG? The tooltip prevents saving otherwise. Also to switch the axes and have
time running along x-axis (which is a bit more traditional) producing a plot
in landscape format? Then the distance north-south in also in an intuitive
direction on the page.

~~~
mbostock
This is my rewrite of a chart I made about 10 years ago (using Protovis, the
predecessor to D3), hence the old data. Back then there were no baby bullets
on weekends!

[http://mbostock.github.io/protovis/ex/caltrain.html](http://mbostock.github.io/protovis/ex/caltrain.html)

If someone wants to collect the new data and send me a suggestion I’d be happy
to update the chart.

~~~
inferiorhuman
What did you use as the original data source? I've been poking at some GTFS
data but there seems to be no obvious way to get distance traveled between
stations (aside from as-the-crow-flies).

~~~
mbostock
Good question. The times were published on Caltrain’s website, but I don’t
recall where we got the distance data; it’s possible the initial
implementation and data collection was done by collaborator, Vadim Ogievetsky.
Wikipedia has track distances:

[https://en.wikipedia.org/wiki/List_of_Caltrain_stations](https://en.wikipedia.org/wiki/List_of_Caltrain_stations)

~~~
inferiorhuman
Ah. I was actually looking at making a similar plot of some other Bay Area
transit agencies. Good to know about the Caltrain distances tho.

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amelius
You could make a 3D version of this chart with all the trains in a country,
which would be more interesting because it can show crossings (the graph in
the article shows crossings but you can't see if there are collisions).

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jakecopp
I'm currently building a realtime Marey diagram chart for Sydney buses to
visualise congestion and bus bunching, feel free to reach out if you'd like me
to let you know when I've shipped a demo!

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jessriedel
What would be the major cost of running the trains twice as frequently with
half the number of cars, especially outside rush hour?

~~~
inferiorhuman
Probably quite high as Caltrain runs into hard limits with their train control
software, they probably don't have that many extra locomotives, and they still
contend with freight traffic.

