Elevator Wait Time Calculator

Average Wait Time is simply half the Interval, and Interval is Round-Trip Time divided by Number of Elevator Cars -- so adding cars always helps, but the model rounds Number of Elevator Cars to a whole number internally, which means a small nudge to it (say, from 4.0 to 4.3) can leave Average Wait Time completely unchanged if it doesn't cross a whole number, even though adding a genuinely new car always lowers wait time. Floors above lobby moves Round-Trip Time (and therefore Average Wait Time) substantially across its whole range. Rated Speed is not a simple "faster is always better" input: a car can only actually reach Rated Speed if a floor is tall enough to accelerate up to it and decelerate again within one floor's travel distance, so the achievable peak speed is capped at the square root of (acceleration x Floor-to-Floor Height) -- both the inter-floor flight time and the per-stop deceleration/acceleration penalty use this same capped speed, never the raw Rated Speed directly. At this calculator's default 3.5 m floor height, that cap works out to about 1.87 m/s, well below the default 2.5 m/s Rated Speed, so the car never reaches its rated speed at the defaults -- and because the cap depends only on Floor-to-Floor Height, Rated Speed has zero effect on Average Wait Time anywhere from about 1.87 m/s up to the 12 m/s maximum; it only starts to matter once lowered below that floor-height-dependent threshold.

Floor-to-Floor Height, by contrast, sets the speed cap itself, so raising it simultaneously lengthens the flight and raises the achievable capped speed (and therefore the per-stop penalty too) -- though at the defaults, Floors above lobby and Car Capacity each move Average Wait Time more per equivalent step. Number of Elevator Cars and Rated Speed are the two inputs that sit on a true plateau at the defaults (integer rounding for cars, the speed cap for Rated Speed), so a small nudge to either can leave Average Wait Time completely unchanged even though both matter over their full range. Service Grade is a stepped 1-5 rating derived from Average Wait Time against fixed CIBSE thresholds (20s, 25s, 35s, 50s), not a continuous scale, so it can stay flat across a range of wait-time changes and then jump a full grade at a threshold crossing.