train terminal vs. station Q.

Factual Questions
1

Would you please settle a bet for me.

HERE’S THE SHORT VERSION:

Without knowing the schedule, if you just show up at a train terminal – the end of a line, where trains often sit and wait for a while before starting their next runs – are you more likely to catch a train in a timely manner (i.e., less likely to miss one by a little bit and have to wait for next one) than you are at a station, where trains just stop momentarily, pick up passengers, and move on?

HERE’S THE LONG VERSION:

My friend Larry and I often take New York City’s uptown “D” subway train from its 34th Street station in Manhattan to Yankee Stadium in the Bronx to attend baseball games.

We arrive at the 34th Street station at slightly different times on different days, since the subways run fairly frequent service, maybe every 5-10 minutes at busy times. We don’t try to follow any train schedule precisely, since the NYC subway just barely follows its own schedule anyway. Like nearly all New York area residents, we don’t even know what the schedule is. When the train comes, we get on it.

Now, normally, the uptown D train runs from Brooklyn into lower Manhattan, stops at several downtown stations and then midtown stations, including 34th Street – where it picks us up – and proceeds uptown (northward) and into the Bronx.

But for some time last year, due to construction downtown (I think), this train line was truncated and it used 34th Street as its southern “terminal.” In other words, it never ran below 34th Street. Each train sat at 34th Street for a while, ran up to the Bronx as usual, came back down to 34th, sat a while again, reversed directions, ran up to the Bronx again …

When this temporary arrangement ended, Larry mourned its passing.

Larry noted correctly that if a train sits at a terminal for a while before leaving on every run, then if you just show up there, you’re likely to find a train sitting there and be able to climb aboard immediately – something that happened to us quite a few times.

But he also says (and still insists to this day), that these circumstances also make it more likely that you’ll “catch” a train in a timely manner, and conversely less likely that you’ll “miss” a train and have to take the next one, so you’re likely to get to Yankee Stadium faster.

I told Larry that was wrong, that arriving at a terminal (the end of a line) vs. a station (a stopping point in the middle of a line) makes absolutely NO difference in whether you’ll “catch” a train or “miss” one.

Boarding at a terminal does offer certain OTHER advantages, which I took great pains to distinguish from the question at hand. For one, you may get to sit calmly and comfortably in a seat on a waiting train while you’re waiting for it to leave, instead of standing on a crowded station platform craning your neck to see if the train’s coming. And if you get a seat early in this manner, you may beat out other passengers who might otherwise have taken that seat for the journey and forced you to stand the whole way.

But you will NOT gain any advantage in “catching” a train, and so you are no more likely to save any time.

MY EXPLANATION: Whether a train is leaving from a terminal, or leaving a station after picking up passengers, it leaves when it leaves. All that matters is whether or not you get onboard before it leaves.

If you get there, say, 10 seconds later, you miss it, and you have to wait for next one to leave, in maybe 5 or 10 minutes. That’s true at a terminal or a station.

If you get there, say, two minutes earlier, and you’re at a terminal, and a train is already sitting there, you can wait onboard the train for two minutes. If you’re at a station, you still have to wait two minutes – it’s just that you’ll be doing it on a platform.

WHO IS RIGHT?

Please, if you answer this question, DON’T answer it quickly or impulsively. Think about it carefully for at least a few minutes.

Thanks,
–The Squid

2

I would say you’re right. The only advantage is that you get to wait on the train instead of the platform. Assuming average headways don’t change, you will, over the course of many trips, wait an average of half the normal headway time for a train to depart.

3

Thanks, that’s one for me … and it helps that you know what “headway” means!

4

I would say your correct. The time it takes for you to get to your destination is (time waiting for the train to leave) + (time taken for travel). The average time it takes a train to leave is independant of how long it waits.

5

the only advantage that you would have in catching a train at a terminal vs at a through station is that some terminals have a leeway in when they depart, usually about 1 minute. Trains that leave Grand Central Terminal are actually scheduled to leave 1 minute later than in the printed and posted schedules, but may leave a minute early if there is no sign of a last minute runner. The last train of the night has a leeway of 3 minutes, and there is staff at the entrances to keep an eye out for runners.

However, in the case of the NYC Subway, they wait for no man. Once the bell goes off and the green signal is given (which BTW DOES usually do a good job of sticking to the printed schedules, assuming the previous train didn’t arrive at the terminal too late) the doors will close whether there are people running down the stairs or not.

6

Yeah, I spoke too broadly about that. In off hours, certainly, the schedule is followed pretty well in my experience, and occasionally some people, including me, will use it to catch trains once in a while.

However, at peak hours (such as rush hours before Yankee games), there’s so much potential for delay that there pretty much always is some, somewhere in the system.

Also, the printed schedules distributed to the public concentrate on when the trains leave terminals and certain stations, giving no specfic times for stations in between.

Due to these factors – and the fact that peak hour service is very frequent anyway – passengers almost universally ignore the schedules and just show up at trackside and wait.

7

Interesting AND useful.

8

Actually, I realized there is an effect that should make average wait times less at the beginning of the run (But, this doesn’t affect average arrival time!).

The idea is that as trains move along the line, they tend to clump together.
This is because simply due to chance, one train will become delayed. Now when it gets to the next station, it will have slightly more than its share of passengers waiting (all those that arrived during the regular interval between trains, plus those that arrived during the delay). Now loading those extra passengers will take slightly longer than normal, so the train gets delayed a little more. Meanwhile the following train has slightly fewer passengers waiting, so its loading takes a little less time, and it gets slightly ahead of schedule (which means it leaves a little early, so there are more passengers for the 3rd train, and it gets delayed…). As you can see, these processes not only build up, but accelerate each other until eventually trains are all in pairs right next to each other, a full train followed by an empty one.
In practice, trains aren’t as affected by this as buses, but it is a real effect.

So what this means is that trains will all leave the beginning terminal equally spaced, but will tend to be slightly clumped in pairs at the middle. The clumping means that a randomly arriving passenger will have a slightly greater average wait time at a middle stop than at the beginning terminal.

However, they both have the same average speed – the beginning terminal guy just spends on average a little less time on the platform and a little more time on average on a train thats going slow because there’s a train right in front of it.

9

That’s because the subway isn’t run like a railroad. There is no specific time that a subway train needs to be at every station. The only specific times on the schedules are when a train departs from its terminal, the station before track where trains must cross each other or merge, and at stations where passengers can connect with another line across the platform (e.g. the A/B/C/D at 59 St-Columbus Circle). If a train gets to a transfer station early, it will usually be held until the schedule (and connecting train) catches up to it, hense the amber-colored holding lights and the dreaded “This train is being held in the station by the train dispatcher, please be patient” announcement.

I’ve found that for the most part, outside of rush hour where trains run so frequently that you don’t even need to check the schedule, the subway is pretty good at sticking to schedule. NYC busses on the other hand…

10

You did remind me of something that does make a terminal vs through station difference. The effect you described is called “train bunching” and happens every day. It’s usually triggered by somebody with an expired metrocard yelling up to the platform to hold the train while he buys a new one, and there’s always some schlump who listens to him, thinking he’s being a good samaritan, when infact he is not only causing the whole line to get messed up due to the delay, but is commiting a violation which carries a $105 fine if noticed by NYPD. Let it happen a couple of times and the train gets delayed enough that there’s another train right behind it which isn’t picking up any passengers while the first train is getting twice as many. When train bunching occurs, the usual MTA remedy to is to do a battery run, which means that the first train will run super express, skipping the next 5-10 stations. If you are waiting at one of the stations skipped by the battery run, then you’re going to have to wait for the second train, where as if you boarded at the terminal, then you were guarenteed to be on the first train.

Of course, the situation works in reverse if you board at the terminal and the battery run skips YOUR destination station :stuck_out_tongue:

11

I can’t speak for certain about the NY subway, but the London Underground certainly does have working timetables (those drawn up for the operation of the system, with far more detail than a public schedule), although these are not published.

12

Many thanks to all for your thoughtful replies.

As a side benefit, I am also learning interesting things about the scheduling of underground urban rail (one of my favorite things, BTW).

I believe I’m safe in assuming that none of the posters here is challenging my original position:

That the typical arrangement by which subway trains often wait for a time in terminals offers no advantage in catching a train to people who choose to board at terminals, and thus offers them no savings in travel time to their destinations, compared with boarding at a station-stop.

Is there anyone who can disprove my position?

13

Well, I can’t agree that it offers NO advantage. You do get your choice of seats, and usually don’t have to RUN for the train if you see it on the platform since odds are it isn’t leaving that very minute, but as far as time and travel are concerned, there is no advantage.

On a related note, the Lexington line in Manhattan is being worked on over the weekends this summer, so that all express trains terminate at Grand Central (the subway GC, as opposed to the railroad terminal which is upstairs). Local trains continue to their regular terminal at Brooklyn Bridge, so that there is only local service between Grand Central and Brooklyn Bridge (express trains normally stop at Union Square and Brooklyn Bridge, skipping all other stations). I find it amusing how many riders on uptown trains, once they arrive at GC, will run across the platform to an express train, not realizing that GC is actually a terminal that day and that their train is going to sit there for the next 5 minutes, meanwhile their local train is halfway to the Bronx before they even leave the station.