Lift Destination Control – Part 2

Traffic Patterns in Buildings

There are three peak periods in office buildings:

• Morning up-peak which is almost exclusively up traffic from the lobby
• Lunch time which has traffic in both directions as passengers leave the building for lunch at the same time as others that may be returning and that left slightly earlier.
• Evening peak as people leave the building at the end of the working day, with almost exclusively down traffic
• Lift Destination Control systems offer greatest efficiency with up-peak traffic.
• It has less marked less marked improvement in lunch time and down peak.
• Although, sophisticated algorithms are becoming available that are improving the situation, particularly at the demanding lunch time peak.
•  One has to bear in mind, with more flexible working hours the traditional most intensive up-peak is actually often less intensive.
• Historically, practically all office workers may have started work at 9 a.m. whereas nowadays they may come to work between 8 a.m. and 10 a.m.
• Several studies have shown that the lunch time traffic is the most demanding on the lift system.

What is Lift Destination Control?

Consider that a group of lifts has a ‘brain’, a central group system control, that takes inputs from the car call buttons in each lift and the landing (up or down) buttons at each landing. It analyses these calls many times a second and dispatches individual

lifts to best respond to those calls.

Now consider a classic situation during the morning rush hour; there are many people waiting for lift service in the lobby, a lift arrives, it fills up and people place their call on the car operating panel. Chances are the lift will stop at more than half of the floors in the building, if not most, as one, or a few people get out at their floor.

What would happen if all the passengers waiting in the lobby input their destination floor whilst waiting for a lift?

The lift ‘brain’ could then analyses those calls, group them, and send lifts to respond. The first lift, let’s call it lift A, would take all those people wanting to go to the 3rd, 4th and 5th floors, lift B would take all those lifts wanting to go to 7th, 8th and 9th and so on. The result is that every lift does not stop at most floors resulting in shorter journey time before the lift can get back down to the lobby to pick up more passengers.

Immediately after a passenger inputs their floor at the lobby terminal they would be told which lift they should take A, B, C etc. they would then go and stand in front of that lift; the result is better order in the lift lobby as passenger go and stand in front of their lift which, in turn allows more efficient loading of lifts a the lobby. This is illustrated in the video below of the lifts in a Hilton London hotel.