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The COVID-19 pandemic has created unprecedented challenges and underscored the ways in which we are connected to one another. Here is a story of how one such challenge -- managing elevator traffic in a classroom building with social distancing -- led to an unexpected collaboration between our mathematics department and facilities division. This issue is not limited to urban campuses with tall buildings, as many campuses across the country operate buildings that are serviced by elevators.
In May 2020, Fordham University convened a working group of faculty members and administrators to study issues related to our learning spaces arising from the COVID-19 pandemic. At that time, two of our predictions for the fall 2020 semester were: 1) that our academic buildings might operate at half of their ordinary capacity to meet social distancing standards and 2) that our elevators might be limited to two passengers at a time.
Our tallest academic building has large elevators that normally hold 25 passengers at once. The discrepancy between those ratios -- half the building population with only one-12th the elevator capacity -- concerned us gravely.
We also confronted great uncertainty around supply chains for new equipment, construction timetables during the pandemic, and finances. We therefore sought interventions that were low cost and did not require the acquisition and installation of new equipment. And we ended up considering four such interventions:
- Assign classes to spaces on lower floors to the greatest extent possible to reduce overall elevator traffic.
- Direct passengers in queues to sort themselves into pairs of passengers with a shared destination floor to reduce the number of requested stops per trip.
- Set one or more cars to follow only car calls, so that these cars can go express from the first floor to upper floors and back.
- Shorten every class by five minutes and stagger half the starting times in each block by five minutes to spread the peak traffic over a larger time interval.
In an article recently published online in Building Services Engineering Research and Technology, I reported on a study I conducted of the effects of those interventions. A university in a large American city that has asked to remain anonymous provided elevator traffic data from an academic building comparable to ours. I wrote a computer program that used those data to simulate elevator traffic as the number of passengers per car varied from two to 12. I simulated the traffic with no interventions, with each of these interventions applied singly and with all four interventions applied simultaneously. I computed standard statistics in vertical transportation research such as the waiting time and transit time (roughly, the time spent waiting in a queue and the time spent traveling in an elevator car, respectively).
The study confirmed many of our predictions. With no interventions and just two passengers per car, we would witness disaster: the queue in the main lobby would exceed its social distancing capacity, the average waiting time would be unacceptably long and many students and instructors would be late to class. In contrast, each of the four interventions improved the elevator traffic, with the greatest effect provided by the fourth intervention. Applying all four interventions at once gave the greatest improvement of all.
Where the study goes beyond confirming our naïve predictions is in quantifying the effects of those interventions. For example, how much more effective is intervention No. 4 than intervention No. 2?
Now we know: with six passengers per car, intervention No. 4 reduces the average waiting time by 43 percent, whereas intervention No. 2 reduces the average waiting time by 6 percent.
And crucially, we learned that if we did receive a rule limiting us to just two passengers per car, we could operate successfully in these conditions by applying all four interventions at once. Building managers seeking to implement low-cost measures to improve elevator traffic under social distancing conditions may look to the percentage improvements described in the article to aid them in selecting interventions appropriate to their buildings.
Ultimately, Fordham University decided to move many classes online for the fall 2020 semester, and we are operating with six passengers per car in our tallest academic building, so our actual conditions for fall 2020 are not nearly as challenging as those used in the study. Nevertheless, it was reassuring to us to know early in the summer that we had the tools needed to deal with a range of conditions we might face. We hope that these research findings may be useful to other institutions with elevators, too, both during the pandemic and after it ends.
