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Understanding Elevator Algorithms and Wait Time Optimization
Key points
- SCAN and LOOK are fundamental elevator algorithms.
- Wait times are measured using distributions like p90 and p50.
- Traffic patterns (e.g., morning rush) significantly affect elevator performance.
- Multiple cars require coordination for optimal efficiency.
Basic Elevator Algorithms
The simplest elevator algorithm, SCAN, patented in 1961, directs the elevator from the lobby to the top floor, then reverses, picking up and dropping off passengers along the way. A more common algorithm, LOOK, only travels as high as the highest requested floor before reversing direction.
Coordinating Multiple Elevators
In buildings with multiple elevators, a central scheduler typically assigns new requests to the closest available elevator. This coordination aims to minimize passenger wait times, though more advanced systems can further optimize this process.
Measuring Wait Times
The effectiveness of an elevator algorithm is often measured by passenger wait times. Simple metrics include the frequency of arrivals within 30 or 90 seconds. More rigorously, the distribution of wait times is analyzed, using percentiles like p90 (90% of waits are below this time) and p50 (half of waits are below this time) to understand the passenger experience, as people tend to remember longer waits.
Impact of Traffic Patterns
Elevator performance varies significantly with different traffic patterns throughout the day. During the morning rush, traffic is predominantly from the lobby upwards, while in the evening, it reverses. Lunch rushes involve mixed traffic, and these varying demands directly influence wait time statistics, with morning rushes often having the longest waits.
✨ This summary was generated by AI from the outlets' reporting listed below. It is not independently verified and may contain errors — check the original sources. How BrevFeed works →
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Reporting from
This article explains the basic algorithms used in elevators, such as SCAN and LOOK, and discusses how wait times are measured and optimized. It highlights the complexity of elevator systems and the factors influencing passenger experience, particularly during peak traffic periods.