Hall Call Allocation or Destination Control Systems for Lifts
Replacing lift car floor buttons with floor buttons on each landing can at first seem an unconventional way to improve traffic performance of lifts. However, these lift control systems have been around for a long time now and it is universally accepted that they can very significantly improve the traffic performance of intensively used groups of lifts.
Destination Control, Hall Call Allocation (there are several names) and hybrid systems are offered by all the major global lift companies and several independent ones for new and modernised lifts.
These lift group control systems can offer dramatic improvements but they have their limitations and they are less suitable to some types of buildings than others.
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 3, 4 and 5 floors, lift B would take all those lifts wanting to go to 7, 8 and 9 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.
A useful analogy to help understand this concept is an Airline company that flies to destinations in Europe; Rome, Paris, Zurich, Madrid for example. It would be ridiculously inefficient if that company flew every plane to every European destination. Instead it knows before the planes take off where customers want to go and it sends one plane to Rome, one to Paris and so on. As there are always more floors in a building than the number of lifts, there is never going to be one lift per floor but ‘grouping’ of lift passengers to close destination floors is a very efficient way of handling this kind of traffic.
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.
Destination controls systems offer greatest efficiencies with up-peak traffic with the 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.
Compared to to the total number of lift systems there are in existance, Hall Call Allocation systems number relatively, a very few and most people have never encountered them. That can lead to confusion for passengers; firstly there are no conventional up-down landing buttons, then when they get in the lift there are no floor buttons (except for some hybrid HCA systems that retain the car buttons).
Some people may figure them out quite quickly and realise that one needs to press the landing buttons for the designated floor but most people would not. We are sure most people would understand what to do given time but we encounter lifts in many different buildings and we expect them to work in a conventional manner.
This leads to the conclusion that the application of these systems will fair better in office buildings where passengers go everyday and once over the inititial change, very quickly become accustomed to how they work. It is of no surprise that practically all of these systems are installed in officee buildings. Buildings such as hospitals, shopping centres, music venues, sports stadiums etc. where the public visit only occasionally are far less suitable for HCA systems. Hotels could be considered a special case as the first place one goes to is the reception desk and that could be a point at which they are instructed on how to use the lifts.
A traffic analysis and/or data logging exercise will allow you to bench mark your existing performance. Further traffic analysis can then be completed to predict the outcomes of future changes, including comparing conventional and HCA systems.
A feasibility study will look at the whole picture, considering the existing lift services and identifying possible options for changing or re-configuring the service to increase the capability of the lift services.
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