10 hours ago
- The simplest elevator algorithm, SCAN (patented 1961), goes from lobby to top floor and back, picking up and dropping off passengers along the way.
- The LOOK algorithm improves upon SCAN by only traveling as high as the highest requested floor before reversing, which matches most people's expectations.
- Multiple elevators coordinate via a central scheduler; the basic method assigns each request to the nearest car, but more sophisticated approaches exist.
- Wait time performance is measured using distribution metrics like p50 (median wait) and p90 (90th percentile wait), as people remember long waits.
- Traffic patterns vary by time of day: morning rush (lobby to upper floors), evening reverse, lunch mix, and inter-floor traffic, affecting wait statistics.
- Smarter algorithms such as Otis' RSR use scoring (anti-bunching, idle nearby) and re-optimize every 5 seconds to improve passenger assignment.
- LOOK can outperform RSR in high flow rates or small buildings with fewer elevators, sometimes simpler algorithms work better.
- Destination Dispatch (kiosk-based) provides full trip information but reduces flexibility, often resulting in longer wait times compared to traditional up/down buttons.
- The complexity of elevator algorithms means that waiting is not personal; the system is constantly optimizing under constraints.