Loading video... VIDEO: The human world is, increasingly, an urban one -- and that means elevators. Two physicists saw this as an opportunity to explore the factors that determine elevator transport capabilities in... view more Credit: Animation: Michael Garfield/Santa Fe Institute The human world is, increasingly, an urban one -- and that means elevators. Hong Kong, the hometown of physicist Zhijie Feng (Boston University),* adds new elevators at the rate of roughly 1500 every year...making vertical transport an alluring topic for quantitative research. "Just in the main building of my undergraduate university, Hong Kong University of Science and Technology," Feng reflects, "there are 37 elevators, all numbered so we can use them to indicate the location of hundreds of classrooms. There is always a line outside each elevator lobby, and if they are shut down, we have to hike for 30 minutes."