Elevators

About

Elevators is a free interactive article that explains why the elevator takes so long, and what is really going on after you press the button. It is a delightful read for anyone curious about everyday systems, for students meeting scheduling algorithms for the first time, and for engineers who enjoy seeing an optimization problem made tangible. What makes it special is that every idea comes with a live simulation you can poke at. Little cars glide between floors as passengers appear, and you can speed time up, change the flow of riders, and watch the wait-time statistics shift in front of you. The piece starts with the classic SCAN and LOOK algorithms, moves on to percentiles and why people remember the worst waits, and then compares Otis's Relative System Response approach with the destination-dispatch kiosks found in newer towers, reaching a few counterintuitive conclusions along the way. It was made by John Herrick and is part of john.fun, his collection of small puzzles, games and projects built for fun. Highlights: • Step-by-step walkthrough of SCAN, LOOK and multi-car scheduling • Live simulations at 1x to 500x speed with adjustable passenger flow • Wait-time histograms with p50 and p90 markers • Traffic presets for morning rush, lunch, evening and interfloor travel • Side-by-side benchmarks of LOOK, RSR and destination dispatch • A full sandbox simulator with configurable floors, cars and algorithm Elevators is completely free, with no account, ads or download. It runs in any modern web browser on desktop or mobile.

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