Why fancy elevator touchscreens often make you wait longer

The fancy kiosk telling you which elevator car to wait for is probably making you wait longer.

An interactive guide by John recently hit the top of Hacker News, breaking down the software that controls elevator banks. It traces the math from 1961's basic SCAN algorithm to Otis's Relative System Response (RSR). RSR scores every car using metrics like passenger load and anti-bunching penalties, then recalculates the best pick every five seconds.

Why it matters: Elevator dispatchers do not optimize for average wait times. They target the p90 case: the bad days with long waits that riders actually remember. Surprisingly, smart Destination Dispatch kiosks—where you select your floor in the lobby before boarding—often increase wait times compared to simple up-and-down buttons. By assigning you a fixed car early, the system loses the flexibility to re-route traffic on the fly.

Here's the gist: complex algorithms beat simple ones during light traffic. But during peak morning rushes when elevators stop on almost every floor, simple logic actually performs better.

Next time you press a hall button, just remember: the system is constantly recalculating behind the scenes.