One Cool Day Job: Building Algorithms For Elevators

McGruber writes "The Wall Street Journal has an article about Theresa Christy, a mathematician who develops algorithms for Otis Elevator Company, the world's largest manufacturer and maintainer of people-moving products including elevators, escalators and moving walkways. As an Otis research fellow, Ms. Christy writes strings of code that allow elevators to do essentially the greatest good for the most people — including the building's owner, who has to allocate considerable space for the concrete shafts that house the cars. Her work often involves watching computer simulation programs that replay elevator decision-making. 'I feel like I get paid to play videogames. I watch the simulation, and I see what happens, and I try to improve the score I am getting,' she says."

Comments

Code that must "never crash", no?

[dryriver]

I'm guessing that the hardest part of the job is writing code that does not crash, possibly leaving elevator riders stranded between floors, or going up when they want to go down. Over the years Otis must have developed a pretty good elevator usage simulator that plays through millions of possible elevator use scenarios, and tries to find one that either crashes or confuses the system. If yes, the developers responsible for that "possibility simulator" should have been named in the article alongside "The Elevator Algorithm Lady". They should have gotten some credit where credit is due...

Mathematician?

[hawguy]

Was a mathematician really needed for this job:

During the recent $550 million upgrade of the Empire State Building, Ms. Christy was asked whether she could help get more people up to the observation deck. She said she couldn't get more people into a car but could move them up more quickly. So she increased the elevators' speed by 20%, to 20 feet per second. Now the cars can rise 80 floors in about 48 seconds, 10 seconds faster than before.

Isn't making the elevator go faster a job for an engineer? Does one really need to be a mathematician to know that a faster elevator moves people faster?

Re:Mathematician?

[vurian]

While you smell like someone who's had an abstract exercise in his first year and now knows everything about the problem area, just because you've never been hired to solve any real problems.

Re:Mathematician?

[samkass]

One fairly new building in south Manhattan has a system where you type the number you want to go to before entering the elevator waiting area, and it tells you what door to wait in front of. When the elevator arrives it lists the floors it will stop at. It seems to optimize for minimal elevator usage, minimal wait times, no overcrowding, etc. Once the elevator system has a little more information it can do a lot better.

Re:Mathematician?

[Idarubicin]

Isn't making the elevator go faster a job for an engineer? Does one really need to be a mathematician to know that a faster elevator moves people faster?

I suspect that the problem here is a failure on the part of the article writer. The author was probably just looking for any sort of answer to 'What's the most famous building you've ever done any work for?', rather than 'what's the most mathematically-interesting part of your job?'

It's also possible that there's a little bit of complexity being glossed over here. For the Empire State Building, visitors take up to three consecutive elevator rides to get to the observation decks: one to get up to the 80th floor, another from 80 to 86 and the main observation deck (though the hearty can take the stairs), and an optional, extra-charge trip from 86 up to the topmost observation area on 102. Visitors form queues for tickets, security, and each elevator ride (both up and down).

While speeding up any of the elevators might seem like a good thing, it runs the risk of causing crowding and bunching of passengers waiting for the now-overloaded next stage. Making one set of elevators faster could increase wear and tear on those elevators (and increase both energy use and passenger discomfort) without improving overall throughput; I can see how there might be some serious mathematical optimization going on there. As well, it's possible that our mathematician was involved in optimizing all of the building's elevator speeds and timings, and not just the elevators dedicated to observation deck service: a much more difficult optimization problem.

Re:maybe they should release it as a game

[Shinobi]

As the parent mentioned, timing involves multiple cars. It's the same thing in optimizing traffic light timings, they can't just factor one direction on a single road. You have to consider parallell roads, crossing roads, highway on- and off-ramp locations and all the traffic loads and the resultant traffic flow patterns. Needless to say, for even a moderate-size city, it's an incredibly complex problem.

Re:maybe they should release it as a game

[Culture20]

It's usually the other way around. The lights are timed for 5-10 miles over the speed limit, and cops use it as a constant stream of speeders for ticketing.

Re:maybe they should release it as a game

[TheLink]

You have to take into account for car locations, direction, speed, where car and hall calls are locatedand have to figure in such things as door times to calculate which car can service a hall call soonest.

I wished more elevators took into account how full they were. There's no point having a full or near full elevator serving external requests. A full elevator should only do internal requests. An elevator might guess how full it is by the load it is carrying, or even whether anyone got in for a previous request (door opened but nobody got in- load stayed the same and is high, but the request button was pressed again soon after the door closed - which normally means there was someone there but he/she did not go in despite wanting an elevator).

Nice to have but not so important would be a standardized way to cancel requests.

Nowadays I think some elevators are on "least energy used" and not "fastest service" at least based on the way they seem to behave...