h a l f b a k e r y
Point of hors d'oevre

meta:

account: browse anonymously, or get an account and write.

 user: pass:
register,

# Subway Sorter

Help passengers to evenly distribute themselves on a subway train
 (+11) [vote for, against]

This is a relatively simple use of data visualization to help subway passengers distribute themselves more evenly into the length of cars in a train. Before the train arrives, illuminated lines in the station floor appear at angles away from the spots where each of the arriving train's doors will be located. Lengths of the lines indicate how much passenger space remains in a car; longer lines indicating that a car has a lot of free space; and shorter or absent lines indicate less or no room. Absolute lengths of the lines indicate approximately how many people can comfortably board that car, assuming the people are standing in line on the line.

Want to get onto an empty car? Wait at the spot with the longest illuminated lines.

The data used to size these lines is collected by sensors on the seats and floors of the approaching train. Sensors in the seats determine how many are occupied, and sensors on the floor count pressure from shoes to roughly estimate how many people are standing (margin of error impacted by heavy briefcases and people with one leg). Further adjustments to the length of the lines come from statistics about passenger exit traffic patterns collected over time.

What dilemma does this "subway sorter" idea solve? The problem at stations I frequent arises from this situation: as the train pulls into the station, some people hastily compare the density of passengers packed into nearby cars and then scramble to get into the cars they judge to be least packed.

Dilemma A: scrambling might result in person-person collisions and, potentially, spilled beverages.

Dilemma B: People can't sort evenly into the full line of train cars because they are limited to scrambling into a small number of nearby cars. This slows down the train's departure because it takes longer to close the doors of a heavily loaded car onto which large numbers of passengers are trying to board.

The basic idea of this "subway sorter" seems pretty obvious to me, so I won't be surprised to find that it already exists in some form or other. Either way, I would like to hear suggestions about more parsimonious methods for estimating the number of passengers per car in the arriving train (RIFD tags?).

[knowtion, Dec 04 2009]

 I like this one. Two or three possibilities for counting load. First, full car image recognition. It's not that difficult to set up a camera to count the number of people in a car. There would be some error, but not that much. Second would be do the same thing, but at the doors. More sensors required, but lower error, just count people in and people out.

Finally, don't count everyone. Just have a group of pressure sensors covering a selection of areas on the floor. Seats will fill up before the floor gets crowded (some people will choose to stand before all the seats are full, but enough will sit before the car is crowded to make this a reasonable assumption). Either do some additional behavioral studies to produce the likely and unlikely standing points, or just scatter 10-20 sensors and go with the probability.
 — MechE, Dec 03 2009

Another one just occured to me. A capacitance or resistance test on the grab bar (for systems where it is grabbed directly, instead of with loops) Voltage to low be felt could be used to estimate how many people are holding onto the bar, giving a decent idea of load.
 — MechE, Dec 03 2009

It's seems so obvious that you would think that someone already thought of it. When I first read the title I thought of it as being some sort of turnstile with a series of mazes that forced you to go to a particular part of the train thus separating friends from their visiting guests or parents from children by the order of a team of social engineers who sit up in a control tower with darkened glass calculating the most efficient method for stuffing people into a rail car. Maybe I just watch too much TV sometimes.
 — Jscotty, Dec 03 2009

[Bigsleep] That actually provides an advantage by shortening station wait times. Since people are more lined up on currently empty cars, there will be less to get in the way of people leaving the fuller cars.
 — MechE, Dec 03 2009

You would also need to account for volume as well as number. Two people carrying a sofa (or couch) take up more space than two people without furniture.
 — Aristotle, Dec 03 2009

[Aristotle], a team with a grand piano would take up even more space. Perhaps the camera system can be equipped with bulky-furniture recognition subroutines?
 — pocmloc, Dec 03 2009

Another (perhaps better) way to implement this would be to put the indicators on the cars themselves. That way the train doesn't have to coordinate or align with the station platform. A car-based indicator would be easier to retrofit as well.
 — phoenix, Dec 03 2009

Very good. Thought provoking.+
 — blissmiss, Dec 03 2009

Most subway systems are computer controlled. Aligning to the platform is not that difficult.
 — Jscotty, Dec 04 2009

[phoenix] But you've got to give people time to prepare for the train coming. You could simplify it by putting a number on the dot-matrix train indicator board which showed the numbers of the train carriages, ordered from least crowded to most crowded so (on the London Underground Piccadilly line) "COCKFOSTERS 17832564 - 2 min".
 — hippo, Dec 04 2009

Large instruments, furniture, and polystyrene farmyard animals in fact wouldn't be a problem. This system only needs to be used during rush hour traffic, when passengers (at least on my local system) are forbidden from toting such bulky items. Although the policy appears to explicitly forbid only bicycles, I guess I'll have to verify this today by asking the station attendant if I could, say, hypothetically bring my giant polystyrene ox to work.

The next generation of trains for London Underground will have load measurement built into the suspension of the train, although, yes, a herd of polystyrene cattle, or a balloon seller, or someone carrying an inflatable sofa would still cause volume/capacity problems. The most difficult part of the system proposed would be the actual installation of the illuminated lines in the platform surface- not technically difficult, but practically difficult.
 — Frankx, Dec 04 2009

You could do the lines with overhead spotlights (shuttered to produce the line segments), which greatly simplifies installation. I'm not sure if it hurts or improves visibility on a crowded platform though. I'd still go with floor mount for new construction, but overhead would simplify retrofit.
 — MechE, Dec 04 2009

What tends to happen is that the middle of the train fills up with people with the first and last carriages being relatively empty. The obvious answer therefore is for trains to go through some sort of clever sidings and junctions between stations which randomly shuffles the order of the carriages.
 — hippo, Dec 04 2009

 // someone carrying an inflatable sofa would still cause volume/capacity problems //

 This is not strictly speaking correct. If the inflatable sofa were actually deflated when carried onto the train it would not be a issue as a deflated unit of this type is very compact. The trouble would come if the passenger subsequently attempted to re-inflate their sofa once the doors had closed and the train moved off. Similar problems might arise from deploying an inflatable liferaft.

 Mitigation of this problem could be achieved by large signs in a number of languages, prominently displayed, and accompanied by voice announcements and suitable graphics, indication that patrons should refrain from inflating furniture on board the train during busy times,

The devil is i the detail, [swimswim] - we are surprised you missed this one ...
 — 8th of 7, Dec 04 2009

Notice: Inflatable watercraft, furniture, and/or farm animals must be deflated during peak transit hours.

Another obvious solution to the counting problem would be to dunk each passenger and his or her parcels in a large graduated cylinder of water prior to boarding and de-boarding the train. This would enable precision counting of each individual and measurement of his or her weight and volume. The above notice would still need to be posted.

"please do not use the escalator when carrying a sofa"
 — po, Dec 04 2009

I realized another flaw with the original description. At many stations, trains on different routes often stop at the same platform. To avoid confusion, the capacity / volume / weight-indicating lines should be multi-threaded, with different colors representing the different incoming trains.

 Use heat sensing camera to count people (and farm animals)...

The people on the platform could be counted this way as well... Numbers along the platform could predict the approx number of empty spots in the car based on the number of people gathered by the car's entrance.
 — knowtion, Dec 04 2009

 This could be self defeating.

 Train consisting of n cars enters station. Some cars display many more free spaces than others. Result ? Most intending passengers head for the "most empty" cars. These then become completely full, leaving passengers on the platform, while other nearly-full cars receive few new passengers.

Individual passengers need to be provided with specific routing information prior to boarding to achieve even distribution.
 — 8th of 7, Dec 04 2009

0.88: people queue on lines of lengths representative of how many more can fit in the car. This allows people to equilibrate by choosing a short line with no people over a long line with too many people. If the lines were instead binary, either on or off, then your described scenario could arise.

//0.88// sp. 1.43
 — shudderprose, Dec 05 2009

 Sorry, [swimswim], I appreciate the idea and I'm not going to bone it, but I don't like it on the grounds that it gives other passengers information... infornation that I could otherwise use to my advantage.

The local knowledge I have of some trains allows me to stand in the right places to maximise my chances of getting a seat (in terms of knowing where the doors will be and also the likelihood of carriage capacity). Your system would bring fairness and balance to all - that's no use to me! ;-)
 — Jinbish, Dec 05 2009

Just be careful saying things like that when the revolution comes. You never know when a Clydesdale might inflate in the seat next to you.