During the holiday travels, one of the vexing things that you might have come across is people in a hurry, those who hurtle by at excessive speed on airport escalators, as you stand. Conversely, you might be the one trying to get back to your boarding area but blocked by a slow traveler carrying an unmanageable volume of luggage bags, more than what one ought to carry on enjoyable trips.
In this article, I return to one of my favorite Operations topics in social behavior. Should people stand left (or right, depending on the country) in moving escalators, so that people in a hurry can walk by? Is that efficient? It turns out not.
It is better for everyone if we do not reserve one side of escalators for standers and the other side for the hurrying crowd.
A fascinating article from Linda Poon at CityLab describes the latest efforts in Tokyo by East Japan Railway Company (JR East) is telling riders it is okay to stand on any side of the escalators inside the city’s busiest transit hubs. As the article reports,
As reported by Japan Times, a study by the Japan Elevator Association in Tokyo found that of the 1,475 escalator accidents in the city between 2013 and 2014, more than 880 were a result of people riding improperly (that includes walking or running on an escalator).
This is certainly true, and it is dangerous for travelers to run on an escalator. But, the reason it is efficient for people to stand on both sides of escalators, is that very few people run!
As CityLab has previously reported, calculations from the engineering manager for Transport for London (TfL) suggested that having everyone stand on both sides of the escalators at Holborn station—one of the city’s busiest—could potentially accommodate an extra 31 people per minute, or 24 percent more passengers. Why? A 2002 theoretical study suggested that when escalators reach more than 60 feet high, fewer people will climb them, leaving ample space to carry standing passengers.
The “nudge” promotions seem to imply it is best people should run to avoid injuries. Standing on an escalator is inefficient precisely because very few people are running and the “running side” is often empty! Putting it another way, if the escalators were always full, with all the people on the stand side standing, and the “run side” running, it would be quite efficient.
Classroom Teaching Example
I will illustrate the escalator capacity usage with an example involving classroom teaching. Suppose that there is a popular course (say, for GRE/SAT or for some certification or credential) for which there is a lot of demand.
One section covers the material at an optimal pace, carefully providing good feedback over two months. This class section is always at full capacity (let’s say that capacity=100 people in the section). Suppose that there is a long list of students waiting for several months to take the class. There is steady learning during the 2-month period and everyone who takes the class passes it. Hence, 100 people graduate every two months.
The second section is a “crash course” section, covering the same material faster and within one month. Say, I design the section for students who want to absorb the material quickly. However, there are few such students and hence this section often runs only 10% of its full capacity (i.e., 10 pupils). Among those taking the crash course, there is a small fraction (say 10%) who overestimate their abilities. They do not end up getting the certification, and hence the pass rate is 90%. Nine students graduate every month.
What system is more socially efficient? Only Regular classes or Reserving a section for the “crash” course?
Two regular sections: Suppose we offer the course in two parallel sections that run for two months. This would graduate 200 students every two months. Surely, it is inconvenient for those who want to take the crash course — those 9 students who successfully take the crash course, but it is beneficial for those who are waiting.
Graduation rate: 200 students every 2 months. No one fails.
One regular section and one crash course: If there is a fast class section and regular class section, the graduation rate would be 100 every two months from the regular section and 9 students every month from the crash course section. (Also note that every month, one student from the crash course does not pass certification).
Graduation Rate: 118 students every 2 months. 2 students do not pass certification.
So, when only regular sections are offered, more people can use the system, although there will be some people that would like to do things faster. Escalators are very much like the above example. It is more efficient to use all capacity and let people stand, which is annoying, of course, for the faster movers.
Does this mean we should prioritize customers?
The problem of Static and “Equal” Allocation.
So, is there no value in priority for people who want to go faster? Of course, there is. But there are two simple issues at play with the escalator and classroom capacity allocations.
The first issue is with the disproportionate allocation, i.e., “equal” capacity allocation for unequal populations. There are quite a few empty seats in the “crash course” when there are people waiting. If there are ten stand-only escalators and one walk-only escalator, we will have better utilization, as there are more standers than walkers. But there is no simple way to split escalators in a ten to one ratio. By standing only to the right and not on the left side, about 50% of the escalator’s capacity goes unused, even as there are many people line up to stand and use the escalator.
By asking to hold the handrails on both sides, cities such as Tokyo & London are trying to utilize unused escalator capacity and move more crowds through the escalators.
The second problem is the static allocation. Standing on one side allocates capacity “statically”. Capacity should be used by standing passengers on both sides – if someone needs to walk by, one just moves over to the right, just like slow cars move over to the right for passing faster cars on highways. Such a polite action would improve utilization.
The principal reason that people stand on one side of the escalator is etiquette. JR East is hoping to moderately nudge the etiquette towards standing both sides and moving over occasionally for walkers passing by.