11 ms·
NYC subway math
- vdnkh 11y agoNice! Really liked the sunk cost part. However, sometimes leaving isn't really a good idea because it's another N minutes to another station, which could take you M minutes farther from your destination than your current train, which arrives O minutes after you get there, which takes P minutes to your stop. For each station, would it be possible to instead calculate the point where (M + N + O + P) < max_wait_time?
- inverba 11y agoUnfortunately this is flawed in a very fundamental way. The NYC subways have different schedules for the morning rush, afternoon, afternoon rush, evening, and night. There should be at least three different distributions in the delay/wait data. Without teasing apart these distributions, I'm not convinced that anything meaningful can be said.
- maxaf 11y agoThe author did limit his "sunk cost" analysis to 7am-7pm due to this exact reason. I think that part at least is quite sound, and is probably the most enlightening takeaway.
- shockzzz 11y agoIt also doesn't take into account the distance between stops. The L train has a short route compared to other lines.
- Judson 11y agoOne other cause of delay (which is, anecdotally, present on the L line) is overcrowding. This is, unfortunately, not shown on the MTA's datafeed, though could maybe be estimated by adding the turnstile data? The morning commute hours (and the hours after a 'delay' status has been cleared) are usually marked by very crowded platforms and trains. Even though the trains are 'on-time' and showing up every 3-5 minutes, there is no room to squeeze on, and you may need to let a few trains pass before getting on one successfully. A 15 minute train 'delay' during the morning commute could cause an hour+ of backed up platforms and people unable to squeeze on. I think this kind of delay is where a lot of the displeasure with L line service is centered.
- apaprocki 11y agoGiven the L's more modern signaling system, they should be able to squeeze more trains on the tracks than they do during the peak rush hour times. I wonder whether they rely on some kind of data that is lagged by a long time period to make those kind of decisions. I'd challenge anyone who contributes to those decisions to ride to Manhattan at 9am and from Manhattan at 6pm for a few weeks.
- danharaj 11y agoI think the L fills a unique enough niche in the subway network that making it run even more will just lead to induced demand. There really ought to be another line between Brooklyn and Manhattan that services parts of the L's route.
- jrcii 11y agoWhere's Ben Wellington when you need him? http://iquantny.tumblr.com/ http://iquantny.tumblr.com/
- iquantny 11y agoRight here!
- whatever_dude 11y agoVery cool website!
- iquantny 11y agoThank you!
- startling 11y ago> My fascination for the subway takes autistic proportions [...] What a weird way to phrase that.
- aarzee 11y agoYeah... Having HFA, I don't really think this is okay.
- deleted 11y ago[deleted]
- kough 11y agoAutism often involves strong obsessions, so it's not wrong. Why does this matter? Fantastic article on the whole.
- liquidise 11y agoSure, but obsessions are hardly the characterizing trait of Autism, nor are they even included in literary definitions. I agree the article is wonderful, but i came to these comments specifically to see if that phrase had given anyone else pause.
- sotojuan 11y agoNo idea if the author intended it this way, but on some forums and imageboards it's normal to refer to being obsessive about something as "being autistic about it". It's similar to how most people call themselves "OCD".
- tedmiston 11y agoIt made sense, but felt distasteful to me.
- mathattack 11y agoWow - thank you for sharing! It's a fun data source for those of us interested in the topic. My son learned numbers and letters from subway stations.
- pjpw 11y ago1. Either the stations are mislabled or that is data from the 1 train not the 4 train in that first visualization. 2. The waiting time by line is flawed because the other lines are redundant to each other (corresponding colors) but the L is a single line so waiting times should be shorter.
- burntwater 11y agoYes, it's the 1 train.
- erikbern 11y agolet me fix
- rgejman 11y agoIsn't the last graph showing a poisson distribution, which is exactly what you expect for situations like "waiting for a train that comes on a schedule"?
- ilzmastr 11y agoYes, one way that the poisson process is defined is as a counting process with inter arrival times that are iid exponentials. The poisson process is the first (continuous time) point process discussed in many textbooks because the counting increments are identically distributed, since the rate parameter is a constant. You can think that in the case of modeling waiting times for subway trains, a better model is with the rate parameter that is dependent on time, since the inter arrival times are smaller during rush hour than when the subway is closed. You can read about this in Bertsekas, and more thoroughly in Parzen or Cox's books on stochastic processes.
- bogomipz 11y agoNice work Erik! You should send this to straphangers.org: http://www.straphangers.org/ http://www.straphangers.org/ No surprise with the L train as its the only one that is automated(despite having a conductor on board.) They refuse to let it run un-manned which begs the question why did they spend the hundreds of millions of dollars to automate the line? There are plenty of places with unmanned subway lines. There's one in Tokyo and I believe Barcelona and Copenhagen. I guess its no surprise that their API would be mess as thats about sums up the culture at MTA from what I can tell. The MTA is spending hundreds of millions of dollar to put arrival clocks in all stations. The problem with is that I want to know how long it is before the next train arrives before I pay for a fare. I have to pay for a fare in order to go onto the platform to find out the next train won't arrive for anther 20 minutes. At this point I have needlessly paid for a fare and generally walk back up stairs and take a taxi. When they were questioned about this poor decision they responded it was because of terrorism that they couldn't put train arrival times outside the entrance. That makes zero sense.
- tedmiston 11y ago> The problem with is that I want to know how long it is before the next train arrives before I pay for a fare. I have to pay for a fare in order to go onto the platform to find out the next train won't arrive for anther 20 minutes. Not to sidestep your question, but do you live in NYC and not use the unlimited pass? I'd assumed everyone did.
- odaymansour 11y agoMy colleagues who live close to work do not own an unlimited card. You've also got people who commute mainly by bike or scooter and only use the subway due to weather conditions or when going out after work/on weekends.
- burntwater 11y agoWhat station(s) are you using that you can't see the time clocks before entering the turnstiles? I can't think of any, although admittedly I'm not looking that often, as I rarely take a taxi for personal use.
- nunez 11y agoDamn. This is useful. I used to just set a timer whenever I waited for a train and left after it expired, but this is really useful data to have too. Good work!
- loisaidasam 11y agoSome thoughts on optimizing for wait time: https://github.com/erikbern/mta/issues/2 https://github.com/erikbern/mta/issues/2
- mwsherman 11y agoAwesome article. The countdown clocks are generally accurate, but in certain situations they are surprisingly off. I would love to see someone use this data to improve arrival predictions – a regression, say, based on features such as time of day (a proxy for crowding), weather, holidays, nearby events (concerts & sports), maintenance or signal problems... I assume the clocks use something as simple a static numbers representing the time between adjacent stations or segments. They presumably don’t tolerate deviations from crowding or other unexpecteds.
- cloudjacker 11y agoInteresting, they should install this calculator on the tablet kiosks in the stations since you wouldn't be able to download this calculator in stations w/o data server
- mrcactu5 11y agoDoes this guy live in New York?? The 4 train does not stop at Van Cordlant-242 St. That would be 1 train. I should know since I ride it every day. http://erikbern.com/assets/4_trips.png http://erikbern.com/assets/4_trips.png