The performance of an elevator is directly related to both the population of the building, and the “arrival rate”; which is the percentage of the population arriving in the lobby to take the lift, in a time frame of 5 minutes (5AR). The other part of the equation is the capacity of the elevator system – i.e. how many passengers the elevator is able to transport from the lobby, within a certain time frame. This criterion is known as the “handling capacity”, which is also defined as a percentage of population in 5 minutes (5HC).
With a well-designed lift system, the Arrival Rate and Handling Capacity are in balance during the most busy time of day (typically morning-peak or lunch-peak). However, when the Arrival Rate is higher than the Handling Capacity, the lift car will get full and some passengers will need to wait the next lift. This means that the system will saturate, and waits will increase exponentially. Similarly, when the arrival rate is significantly lower than the handling capacity, the system is overdesigned – at the expense of high costs (too many lifts) and a poor design efficiency (building core too large, too many lift shafts).
The most important indicators of ‘quality of service’ in Elevators are:
- Average Waiting Time (AWT); the average of all passenger who are using the elevator, departing from any floor in the building.
- Average Time To Destination (ATTD); the time it takes from the moment of arriving in the lobby until reaching the destination floor.
- Average Car Load Factor (ACLF); the average fill rate of the lift car
The above performance indicators can only be determined through a Traffic Simulation.
Traffic Simulations and Analysis is typically required during design stage of a new building, during a lift modernization project, and in case of traffic complaints (long waits and full cars) with existing buildings. Designing and dimensioning elevators is a careful balance between Space, Performance and Costs.
Traffic Simulation and Analysis
Traffic Simulation and Analysis
- On-Site Measurements of Traffic Performance
- Traffic Simulation and Analysis
- Traffic Report and Recommendations
When users in existing buildings suffer from too long or excessive waiting times, or very full lift cars, it is important to measure and verify the elevator settings and adjustments (lift speed, acceleration, deceleration, jerk, door open- and close speeds, start delay, sensor delay, etc), and check against the design criteria. In some cases the Elevator Monitoring System will provide a good source of information and may provide more data on the performance which can be checked. Deviations in the system or controller settings can bring immediate improvement in the system performance. If those improvements are not sufficient, the next step is to conduct traffic simulations and analysis.
Traffic simulation and analysis will allow help to understand the performance of your vertical transportation system. Based on actual measurements on-site, or the expected passenger flows and profiles as per design and expected usage (up-down and inter-floor), we will simulate the elevator system performance for the several lifting strategies or lift configurations, and any proposed improvements in the system design. We use the latest and most sophisticated traffic simulation software, including software developed in-house.
We will prepare a detailed Traffic Analysis report with executive summary and result tables, and all relevant graphs. We will compare the traffic performance of the elevator system with relevant regional or global performance criteria, such as Chartered Institution of Building Services Engineers (CIBSE Guide D), British Council for Offices (BCO - Guide to Specification), Property Council of Australia (PCA - a Guide to Office Building Quality).
