Lift Traffic Analysis: The Foundation of Every Vertical Transportation Project

Lift traffic analysis is the discipline that sits at the heart of vertical transportation design. It provides the analytical framework that allows engineers and consultants to answer the core questions: how many lifts does this building need, how should they be configured, and will they actually meet the performance expectations of the people who will use them?

Every multi-storey building presents the same fundamental challenge: people need to move between floors efficiently, and the systems that enable that movement must be specified, sized, and configured correctly before a single floor plate is laid. Get it right and the building works as intended for its entire operational life. Get it wrong and the consequences, longer wait times, congested lobbies, complaints from occupants, and the significant cost of retrospective remediation, persist for decades.

What Lift Traffic Analysis Actually Measures

Traffic analysis in the context of vertical transportation is concerned with the flow of passengers through a lift system over time. The primary metrics are handling capacity, which measures the percentage of the building population that a lift system can serve during a given peak period, and average waiting time, which measures how long passengers typically wait before boarding a lift.

A third metric, average journey time, measures the total time from a passenger pressing the call button to arriving at their destination floor. Together, these three metrics, handling capacity, average waiting time, and average journey time, provide a comprehensive picture of how a lift system will perform under representative conditions.

The challenge is that these metrics are not fixed. They change depending on the time of day, the occupancy pattern of the building, the distribution of passengers across floors, and the behaviour of the lift system in response to varying demand. This dynamic complexity is why manual calculation methods, which rely on simplified assumptions and average-case scenarios, are increasingly inadequate for modern building design.

The Case for Simulation-Based Analysis

Simulation-based lift traffic analysis uses computational models to replicate the behaviour of passengers and lift systems under realistic conditions. Rather than calculating a single average-case performance figure, simulation allows engineers to test how a proposed lift configuration performs across thousands of simulated scenarios, capturing the full range of variability that characterises real building use.

The Monte Carlo simulation method, which is used in the most rigorous traffic analysis tools, generates large numbers of simulated passenger journeys with randomised characteristics drawn from probability distributions based on observed building behaviour. The results of these simulations provide not just average performance figures but confidence intervals that allow engineers to understand the range of outcomes the system might produce.

This probabilistic approach is particularly valuable for buildings with unusual occupancy patterns, mixed-use developments where different user groups have very different peak demand profiles, or high-density buildings where small variations in lift configuration can have large effects on performance.

Common Lift Traffic Analysis Scenarios

Traffic analysis is most commonly conducted for three standard scenarios: up peak, which models the morning arrival period when demand is concentrated in one direction; down peak, which models the departure period; and interfloor, which models the midday period when demand is more dispersed.

For many building types, the up-peak scenario is the most critical, as it typically produces the longest waiting times and places the greatest demands on the lift system. However, for buildings with significant midday footfall, such as mixed-use developments with retail or restaurant facilities at ground level, interfloor performance can be equally important.

Modern simulation tools allow engineers to model all these scenarios and to adjust the parameters to reflect the specific characteristics of the building under analysis. This includes the floor-by-floor population distribution, the start and end times of the peak period, the average passenger interarrival rate, and the specific lift parameters, including car size, speed, door timing, and control algorithm.

What Good Lift Traffic Analysis Software Provides

Specialist lift traffic analysis software should provide several things. First, a robust simulation engine that accurately models both passenger behaviour and lift system operation. Second, an expert system that can generate recommended configurations based on the building parameters, giving engineers a starting point to refine rather than a blank page to fill. Third, professional-grade output that can be included directly in design documentation and presented to clients.

Lift traffic analysis is the core capability that separates specialist vertical transportation tools from generic engineering software. Engineers who adopt a simulation-based approach to traffic analysis produce more defensible specifications and deliver better-performing buildings.

Integrating Traffic Analysis Into the Design Process

The most effective approach to lift traffic analysis is to integrate it early in the design process, when changes to the lift specification can still be made without high cost or programme implications. Analysis conducted at the feasibility stage, when the fundamental questions of lift quantity and configuration are still open, provides the greatest value.

Successive rounds of analysis through the design stages, each with progressively more detailed building parameters, allow the lift specification to be refined iteratively as the project develops. This approach is far more effective than a single analysis conducted late in the design process, when the specification may already be partially fixed, and the scope for optimisation is limited.

Engineers who bring simulation-based analysis into their projects early, and who use the results to drive design decisions rather than simply to confirm them retrospectively, deliver better-performing buildings and provide their clients with a more defensible and transparent specification process.

According to CIBSE Guide D, the industry standard reference for vertical transportation design in the UK and widely referenced internationally, simulation-based methods are now the recommended approach for lift traffic analysis in complex or high-density buildings.

 

The Value of Getting It Right

AdSimulo lift design combines simulation with an intelligent expert system to give engineers rigorous traffic analysis with professional reporting built in. Lift systems are expensive to install and nearly impossible to remediate once a building is occupied. A lift lobby that is too small, a system with insufficient capacity for peak demand, or a configuration that produces unacceptably long waiting times during the morning rush are problems that building owners must live with for decades.

The cost of thorough traffic analysis, by contrast, is a fraction of a percent of the total cost of a building's vertical transportation system. It is one of the highest-value engineering activities available in the design process, and one of the most straightforward to justify on a pure cost-benefit basis.

For engineers and consultants who take vertical transportation seriously, simulation-based lift traffic analysis is not an optional add-on. It is the foundation on which every other design decision rests.