Boston Subway Time-Scale Map

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Boston Subway Time-Scale Map

Postby Adams_Umass_Boston » Tue Aug 28, 2012 4:45 pm

A friend sent me this design from Stone Brown Design.

The designer took the time between stations to draw out the T spider map.

What do you think?

http://www.stonebrowndesign.com/boston-t-time.html
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Re: Boston Subway Time-Scale Map

Postby Yellowspoon » Sat Sep 01, 2012 8:13 pm

Not very realistic: one minute from Newton Center to Newton Highlands. One minute from Highlands to Eliot. Thence four minutes from Eliot to Waban. In reality, they're all 0.8 miles apart, which would make the trip from Newton Center to Eliot average 75 MPH, including the stop at Highlands.
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Re: Boston Subway Time-Scale Map

Postby 3rdrail » Sat Sep 01, 2012 10:34 pm

Interesting concept, but I suppose that there would be a danger in trying to "fit" within a certain pattern, thus skewing the actual data. Also, you'd really have to sit there on a car with notepad and stop watch to do every individual stop in succession - probably a number of times, to have it actually be accurate. Not an easy project, but would make a great Master's thesis. (Probably why we haven't seen it before.)
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Re: Boston Subway Time-Scale Map

Postby Arborwayfan » Sun Sep 02, 2012 1:27 pm

The designer says he used the scheduled times; the oddity Yellowspoon noticed is probably because whoever made the schedule set it up to have make-up time between Eliot and Waban. Six minutes for 2.4 miles is about right, no? I assume no one ever wants the Green Line cars to have to wait for a scheduled departure time, so they set them up to be running a minute or so "late" all the time so they can just leave when they get there. As a tranportation engineer explained it to me once, on a busy transit system where no one is looking at the schedule or caring about being a minute or two "late" you set up a schedule to show what can usually be done, and then most days you actually get in one or two extra runs. So even if some cars are theoretically late most people get to their destination a little sooner.
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Re: Boston Subway Time-Scale Map

Postby MBTA3247 » Sun Sep 02, 2012 3:50 pm

Arborwayfan wrote:As a tranportation engineer explained it to me once, on a busy transit system where no one is looking at the schedule or caring about being a minute or two "late" you set up a schedule to show what can usually be done, and then most days you actually get in one or two extra runs. So even if some cars are theoretically late most people get to their destination a little sooner.

Some systems may well run that way, but not the T. All buses and trains have scheduled departures, so even if a run is completed early, they have to wait before making their next trip in the opposite direction. There are no "extra" runs.
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Re: Boston Subway Time-Scale Map

Postby 3rdrail » Sun Sep 02, 2012 5:21 pm

MBTA3247 wrote:
Arborwayfan wrote:As a tranportation engineer explained it to me once, on a busy transit system where no one is looking at the schedule or caring about being a minute or two "late" you set up a schedule to show what can usually be done, and then most days you actually get in one or two extra runs. So even if some cars are theoretically late most people get to their destination a little sooner.

Some systems may well run that way, but not the T. All buses and trains have scheduled departures, so even if a run is completed early, they have to wait before making their next trip in the opposite direction. There are no "extra" runs.

Derek, that's just plain wrong. I'll just use the T as an example, but they've been running and truncating extra and limited runs for as long as I can remember. "Fill-in" runs are definitely more often than "extra" runs due to the nature of headway on the lines, which if on schedule, will cause "extra" cars not to be needed. It's when the schedules are broken where you see extra runs that may not have been part of the original headway force. For example, the Orange Line used to occasionally (rarely) get a mechanical malfunction causing the cars to stop running in both directions. A supervisor would give the order and the red "A" would go on the left front window meaning that the car was a limited. For cars coming out of the Hills, they'd usually run express to Dudley or even Washington (Xing). Similiarly, cars up the line at Dudley would run to Washington etc. etc. in order to try to get ahead of the schedule loss and in doing so, these cars would be lost to their normal runs. The gap left by the "limited" would have to be made up, so extra's would be deployed, or cars sent ahead before schedule would be launched. The bottom line is that show me a system that doesn't do exactly what Arborwayfan said does and I'll show you a fantasy railway. They all run this way because slowdowns or stalls are inevitable and the slack must be taken up.
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Re: Boston Subway Time-Scale Map

Postby Arborwayfan » Mon Sep 03, 2012 11:17 am

Paul and Derek, we've actually got three separate ideas going on here:

1. The schedule may be designed with unrealistically short times between some stations so that a train can depart most stations whenever it's ready without waiting for the schedule (because it's on time or already late) and unrealistically long times between others so that a train makes up its time and departs most stations more or less on time.

2. The T expresses trains when they are way behind schedule and adds fill-in runs or extra trains to recover from mechanical failures (or heart failures -- I was once on the OL when it was delayed several minutes at Egleston or Green for one of those, after having run express to Dudley). Derek hasn't said the T doesn't do that.

3. Some transportation engineers say that systems should push trains through the system faster than the schedule calls for when that's possible, as a matter or routine, not just to make up for delays, even if it means most trains are not running exactly on schedule. Derek says the T doesn't do that. I wasn't sure the T did do it.

I put 1 and 3 in the same paragraph because I thought they might both be going on, but 1 could be true and 3 false, or vice versa. I'm sorry for that confusion.

I love thinking through these questions with you guys (and the rest of the board) -- and I am not pulling rank as Derek's former professor. :)

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Re: Boston Subway Time-Scale Map

Postby 3rdrail » Mon Sep 03, 2012 12:14 pm

Honestly, I'm not following your or Derek's points here. I'm going to have to go back and recall my logics classes (it's been a long time), so here we go;

"Some systems may well run that way, but not the T."
(That implies that the T either doesn't have breakdowns, or doesn't compensate scheduling to make up for time and mileage lost on a particular line by bringing out what would be unscheduled service. We know that the T does both.)

If..."All buses and trains have scheduled departures", then only "scheduled" departures take up slack when an obstruction is cleared.
(We know that this is simply not the case. Any operator will tell you that.)

"...so even if a run is completed early, they have to wait before making their next trip in the opposite direction."
(Not if directed by a supervisor to pull out ahead of schedule to fill in a gap, which is a regular occurence.)

"There are no "extra" runs."
(This is another one of those flat out "never happens" eliminators. As proof of this not being the case, I suggest that by it's very definition, a train pulled out early from it's am or pm rush schedule, is an "extra run". It happened all of the time on the El, most noticeably when a train of Wasons would show up before the pm rush to get the line of Pullmans in synche after a stall (medical emergency, police action, or breakdown).

I'm having a flashback now telling me that I have to be at the Knowles Center at 8AM for a big exam - got to go !
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Re: Boston Subway Time-Scale Map

Postby MBTA3247 » Mon Sep 03, 2012 1:54 pm

Ok, my interpretation of Arborwayfan's comment about getting extra runs in is that by running faster than schedule and departing endpoints immediately after arriving and loading/unloading passengers, operators can get in an extra run before their shift ends. That, I know doesn't happen on the T: every operating assignment (except, I guess, the RADs on the Green Line) has a given set of departure times from a route's endpoints, so if a train or bus gets to the end of a trip early, it has to sit and wait for its next scheduled departure. The closest thing to operators getting extra runs is that the bus dispatchers regularly make calls on the radio looking for drivers who have almost finished their assigned runs to substitute for an absent driver on another route and get some extra hours in. (I don't know if similar things occur on the rapid transit lines)

Note that the above applies to regular operations only. How the T handles extra or terminated trips when the schedule gets completely and utterly trashed I don't know. My experience with expresses, though, is that the express is a regular trip that has become so late it needs to run express to make up time, and the local following it is also a regularly scheduled run (though probably running late because of the previous train being late).
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Re: Boston Subway Time-Scale Map

Postby Arborwayfan » Mon Sep 03, 2012 4:19 pm

3rdrail, I'm not sure I exactly understand what I wrote. :) I'll try again.

Derek's got my 2 and 3 right: 2 says that the T and many other systems use expresses, diversions, RADs, unscheduled short turns, etc., to recover from problems. That's what you said, and you're right.

3 says a system with very short headways could ignore the schedules and squeeze in a couple extra trips every day, by letting trains leave early; Derek says the T doesn't and I assume he's right. My planner acquaintance many actually have said this: On a system with very short headways (2 minutes, say, like Santiago, Chile, or the Central Subway if it were all one route), schedule trips so fast that you know they will be a minute or so late fairly often and you might have to cancel one some days. If you manage to keep the schedule half the time, passengers are better served when you do keep it, and when you can't keep it, the passengers are no worse off than they would be if you didn't try.

This started with Yellowspoon's comment: "Not very realistic: one minute from Newton Center to Newton Highlands. One minute from Highlands to Eliot. Thence four minutes from Eliot to Waban. In reality, they're all 0.8 miles apart, which would make the trip from Newton Center to Eliot average 75 MPH, including the stop at Highlands."

The mapmaker said they used the published schedules to make the map. If that's right, then the scheduled times for train leaving Newton Ctr at 12 would be Newton Highlands 12:01, Eliot 12:02, and Waban 12:06.

I was just guessing that maybe the T wrote the schedule that way to build in time to allow late trains to catch up. Maybe they know that if a train leaves Newton Ctr at 12 it will usually be ready to leave Waban at 12:06, but they don't know where it will spend that time. Some trains maybe have a long stop at Eliot, others a long stop at Newton Highlands. With this schedule, no train will ever have to wait for its scheduled departure time at Newton Highlands or Eliot, because every train will always be late there -- but by a minute or so so no passenger will ever notice. By the time they leave Waban, they'll be on time again, no matter which station they had the long stop at. Amtrak does this with its trains from Carbondale to Chicago -- they are almost always a little late in Effingham and Champaign-Urbana, and almost always within a couple minutes of on-time into Chicago. I think some T commuter schedules have similar make-up time between Back Bay and South Station, or used to, right? On the GL the trains are a lot more frequent and the times are shorter, but it's the same basic idea.
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Re: Boston Subway Time-Scale Map

Postby 3rdrail » Mon Sep 03, 2012 6:20 pm

Guys- We all know what we're talking about. Let's just leave it at that. There really isn't a point to be made here and we could go back and forth on this all night. Eventually, we would be disputing the color of the El's girders between bohemian brown, givenche grey, and my particular favorite, ornery oyster. I did enjoy the back and forth but on this one, I just don't think that there is enough substance. Good discussion though.
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Re: Boston Subway Time-Scale Map

Postby Arborwayfan » Wed Sep 05, 2012 12:52 pm

Thanks, 3rdrail. I needed that.

Simple question for anyone: How well do trains/cars on the various lines keep their schedules?
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Re: Boston Subway Time-Scale Map

Postby MBTA3247 » Wed Sep 05, 2012 8:01 pm

I want to say that most of the time everything is on schedule, but it can be something of a crapshoot. And once a given bus or train is more than a few minutes late, it'll be late for the rest of its assignment.

However, for the last runs of the night... *walks away laughing maniacally* :wink:
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