Comments on: Buses are bosons, and they condensate

By: Mike Maxwell

Mike Maxwell — Wed, 17 Mar 2010 01:30:53 +0000

And in Euclid’s time, the Earth was flat, so of course Riemann geometry was not applicable; ergo no way Ύδε πάρκ ΒόυλεΒαρδ could have intersected Ύδε πάρκ ΒόυλεΒαρδ!

By: Anne

Anne — Wed, 17 Mar 2010 00:40:53 +0000

My memory worked a lot better back then, too.

By: Mike Maxwell

Mike Maxwell — Tue, 16 Mar 2010 23:36:19 +0000

Anne, this is Riemann geometry. Not only do (South) Hyde Park Blvd and 55th intersect, it appears that (South) Hyde Park Blvd and (East) Hyde Park Blvd intersect.

I’m sure bus routes were much simpler in Euclid’s time.

By: Anne

Anne — Tue, 16 Mar 2010 22:26:05 +0000

In my memory, Hyde Park Blvd. and 55th were parallel, so for a simpler mathematical account of why you waited so long for the Jeffery to arrive at the corner of those two streets, look to Euclid’s Definition 23.

By: Paul Kaplan

Paul Kaplan — Fri, 12 Mar 2010 01:25:15 +0000

I’m an undergraduate physics major at the University, and just so you know the 6 is the “Jackson Park Express” not the Jeffrey express!

GO UCHICAGO!

By: Jimmy James

Jimmy James — Wed, 10 Mar 2010 15:23:01 +0000

I remember this problem appearing in my continuum physics class when we were discussing shock waves- I think the professor found it in Tritton’s Physical Fluid Dynamics.

Speaking of things condensing like bosons, there was a good joke during a statistical mechanics midterm- the TA thinks everyone’s too bunched together, so he says, “No, no! You guys should be like fermions! Spread out a bit!” Some wiseguy says, “If we’re fermions, should we not put our names on the test?”

By: Charon

Charon — Mon, 08 Mar 2010 21:51:21 +0000

Erratum:

“the buses were scheduled to run every 15 minutes”

No, they weren’t. My recollection was every ~6 minutes at peak (I’m remembering this from 8-10 years ago, when the #6 was the Jeffrey, probably about when you were there). Currently the CTA site says it arrives every ~8 minutes (5-12, depending on the time of day).

By: Neal J. King

Neal J. King — Mon, 08 Mar 2010 11:13:39 +0000

So it seems like there are a few driving-policy changes that would eliminate this bunching effect.

Any possibility of communicating them to the management of the bus system?

By: Katy Huff

Katy Huff — Mon, 08 Mar 2010 03:08:14 +0000

Sean, perhaps it’s been too long since you were in HP! The Jefferey is the #14. The #6, which goes to downtown, is the ‘Jackson Park’ Express.

Anyway, the rest of this post is right on target! I was there this weekend and, I kid you not, witnessed (from the third bus) three #6 buses converge on 55th street and Hyde Park Blvd.

By: ChicagoMolly

ChicagoMolly — Sun, 07 Mar 2010 19:03:11 +0000

It’s more complicated than that. What with street repairs, wheelchair passengers, and nannies with those enormous SUVStrollers, buses can start to bunch up. The drivers will sometimes leapfrog each other if they don’t have passengers who need to exit at a certain stop, but they’re not supposed to. The route schedules tell the drivers what time they’re supposed to make each stop, and CTA sends supervisors out every day running spot checks to ensure that drivers are sticking to their schedules. If the drivers are leapfrogging, and Bus #2 meets up with a supervisor while he’s ahead of Bus #1, the driver will have to wait for the other bus to get ahead of him, and if he’s significantly off-sched may have to wait a few minutes more to get back to the proper spacing. Over the long haul it does really average out, but when you happen to be on the bus that gets held back (and you’re running late for work) you want to scream something impolite.

By: Kaleberg

Kaleberg — Sun, 07 Mar 2010 03:46:45 +0000

I remember this from probability class. There are two Poisson processes involved. The one for the buses and the one for passengers. Even without clumping effects, there were always more passengers stuck waiting longer periods than one might expect.

If you throw in the delay feedback problem, it just gets worse.

If we had reliable information about bus arrivals, more people might wait for the next, less full bus, but for most passengers, “There’s a bus right behind this one” translates as “The check is in the mail.”

By: Shaun

Shaun — Sat, 06 Mar 2010 19:32:29 +0000

In other words, buses really do arrive according to a Poisson process

By: emeris

emeris — Sat, 06 Mar 2010 16:24:40 +0000

I would just point out that the 6 is now called the jackson park express (http://www.transitchicago.com/riding_cta/busroute.aspx?RouteId=165)

By: Jeb

Jeb — Sat, 06 Mar 2010 16:01:34 +0000

What is most annoying to me about this phenomenon is that half the people don’t just wait two seconds for the other bus

By: gopher65

gopher65 — Sat, 06 Mar 2010 04:27:08 +0000

Jdhuey: I live in Saskatoon, Canada, and I’ve made the same observation. In Daniel’s model the fast buses cause much of the bunching. Here, when a bus is running fast, they’ll just sit at a stop for a couple minutes. This prevents bunching from ever happening (except near the university, where there are several buses a minute pulling in and leaving during peak times. But that’s different.).

By: spyder

spyder — Sat, 06 Mar 2010 01:45:53 +0000

I guess this is a Chicago, NYC sort of problem, not experienced by me in any of the regions i have lived over the last sixty years. Santa Monica Transit ran just fine in the 60s and 70s, Alameda County worked wonderfully with SamTrans in the late 70′s and early 80s, Spokane is just perfect in the 21st century.

By: Travis Garrett

Travis Garrett — Sat, 06 Mar 2010 00:11:42 +0000

Comment 9:

When You
observe bubble chains in champagne or gazified water starting
at some point in the glas, You sometimes will find such strings
made up from pairs of bubbles moving closely connected.
Georg

pretty much sums it all up doesn’t it?

By: Jdhuey

Jdhuey — Fri, 05 Mar 2010 23:57:06 +0000

Well, I have only a limited experience riding the public transit light rail/ bus system here in San Diego County but I noticed that, at least on the routes that I took, the timing was very punctual. I also noticed that the bus drivers were very careful not to get off of their schedule – but mostly they made sure they didn’t get *ahead* of schedule. On many occasions, the driver would just sit at the bus stop until the official clock on the dash hit the right time. I suspect that buses that get ahead of schedule can cause just as much of a disruption as buses that get behind.

By: steeleweed

steeleweed — Fri, 05 Mar 2010 23:46:14 +0000

Once saw the math explaining why elevators are never on your floor or headed in your direction. I vote for ‘the universe is conspiring’ theory.

By: Oana

Oana — Fri, 05 Mar 2010 20:07:50 +0000

We now have CTA bus tracker here in Chicago, so no need to wait more than a couple of minutes. It’s purely amazing, especially in winter.