Lift Traffic Analysis and Selection

A Complete Guide for Architects

1. Introduction

Lifts are essential components of vertical circulation in residential towers, office buildings, hotels, hospitals, shopping centres, and other multistorey developments. Their performance influences how people move through a building, how comfortably they reach their destinations, and how efficiently the building’s circulation system operates.

Selecting a lift is not simply a matter of deciding its rated capacity or speed. A building may have several lifts and still experience long queues if passenger demand is concentrated at particular times or if the lift group is poorly configured.

Lift traffic analysis is the process of evaluating expected passenger movement and assessing whether a proposed lift installation can serve that demand at an acceptable level of service.

For architects, this analysis should begin during concept design, when the number and location of lift shafts, the building core, lobby dimensions, and circulation arrangements can still be adjusted.

The international standard ISO 8100-32:2020 addresses the planning and selection of passenger lifts in office, hotel, and residential buildings. It covers calculation-based and simulation-based approaches, with the standard confirmed as current in 2025.

ISO

This guide explains the fundamental principles, key calculations, selection criteria, architectural coordination requirements, and limitations of preliminary lift traffic analysis.

2. What Is Lift Traffic Analysis?

Lift traffic analysis is a technical assessment used to determine whether a proposed lift system can transport a building’s expected passenger population efficiently during periods of high demand.

It considers factors such as:

• Total building population and occupancy distribution.
• Number of floors and floor-to-floor heights.
• Number of lift cars and their rated capacities.
• Rated speed and acceleration characteristics.
• Door opening, closing, and passenger transfer times.
• Passenger arrival patterns and destinations.
• The number of stops made during a typical journey.
• Expected waiting time, handling capacity, and journey time.

The analysis helps the design team compare alternative lift arrangements before finalizing the building core.

Why is lift traffic analysis important?

It helps to:

1. Estimate the number of lifts required.
2. Assess the capacity of the proposed lift group.
3. Determine whether the selected speed is suitable.
4. Evaluate expected service during peak demand.
5. Reduce the risk of excessive waiting and overcrowding.
6. Avoid unnecessary expenditure on oversized or excessive lift installations.
7. Coordinate lift planning with architectural, structural, electrical, and fire-safety requirements.

The aim is not necessarily to install the maximum possible number of lifts. It is to provide a system that meets the defined passenger demand and service criteria without wasting valuable floor area or capital.

3. Fundamental Principles of Lift Traffic Analysis

Four performance concepts are particularly important: handling capacity, round-trip time, interval, and waiting time.

3.1 Handling capacity

Handling capacity measures how many passengers a lift group can transport during a specified period under defined traffic assumptions.

In conventional up-peak analysis, it is commonly expressed as the number of passengers carried in five minutes or as a percentage of the building population served during that period.

The percentage form is:

\[ HC\%=\frac{300PL}{RTT\times U}\times100 \]

Where:

• \(HC\%\) = handling capacity as a percentage of building population.
• \(P\) = assumed average passenger load per departing car.
• \(L\) = number of lifts in the group.
• \(RTT\) = round-trip time in seconds.
• \(U\) = relevant building population.
• \(300\) = duration of five minutes in seconds.

This expression assumes a consistent average passenger load and repeated round trips. Actual handling capacity depends on traffic patterns, control strategy, and operating conditions.

Architectural significance: A lift group must be capable of serving the expected demand during the selected peak period. Its rated capacity alone does not establish whether it will perform adequately.

3.2 Round-trip time (RTT)

Round-trip time is the estimated time taken by a lift to complete a representative journey under a specified traffic model and become available for the next comparable journey.

In conventional up-peak analysis, it accounts for:

• Upward travel.
• Intermediate stops.
• Passenger boarding and transfer.
• Door operation.
• Reversal at the uppermost stop.
• Return travel to the entrance level.

A simplified form of the conventional round-trip equation is:

\[ RTT=2Ht_v+(S+1)t_s+2Pt_p \]

Where:

• \(H\) = average highest reversal floor, expressed in floor intervals.
• \(t_v\) = average travel time between adjacent floors.
• \(S\) = average number of probable stops.
• \(t_s\) = time associated with stopping.
• \(P\) = assumed passenger load.
• \(t_p\) = average one-way passenger transfer time.

The precise definitions and calculation procedures must follow the selected methodology. This equation is a simplified planning model, not a substitute for the complete method in CIBSE Guide D or ISO 8100-32.

Architectural significance: RTT helps explain why the same lift capacity may perform differently in buildings with different heights, stop patterns, door timings, and passenger loads.

3.3 Lift interval

Interval is the average time between successive departures from, or arrivals at, a designated point in a lift group under the specified traffic model.

For a simplified group of identical lifts operating under conventional up-peak assumptions:

\[ I=\frac{RTT}{L} \]

Where:

• \(I\) = average interval in seconds.
• \(RTT\) = round-trip time in seconds.
• \(L\) = number of lifts.

For example, a calculated RTT of 120 seconds for a group of four identical lifts gives a theoretical interval of 30 seconds.

This is an illustrative calculation, not a recommended interval for every building.

Important: Interval is not the same as actual passenger waiting time. Real waiting times depend on passenger arrival patterns, lift control, traffic distribution, and service interruptions.

3.4 Passenger waiting time

Waiting time is the period between a passenger arriving at a lift landing and the lift becoming available for boarding.

It is affected by:

• Passenger arrival patterns.
• Lift availability and dispatching.
• Lift-group size and capacity.
• Door dwell time.
• Traffic distribution among floors.
• Destination-control or conventional control systems.
• Temporary congestion and lift outages.

Average waiting time, interval, and journey time should be considered together rather than treated as interchangeable performance measures.

4. Types of Lift Traffic Patterns

Different buildings experience different passenger movements. Identifying the likely traffic pattern is essential to selecting the correct analysis method.

Traffic pattern	Typical characteristics	Relevant building examples
Up-peak	Large numbers of passengers travel upward from the entrance level	Office buildings at the start of the working day
Down-peak	Large numbers of passengers travel downward towards the exit	Offices at closing time, some event venues
Interfloor traffic	Passengers travel between intermediate floors	Hospitals, hotels, mixed-use buildings
Two-way traffic	Simultaneous upward and downward movements	Residential buildings, commercial developments
Lunch or midday peak	Demand increases around dining and shared facilities	Offices, campuses, hotels
Special-event traffic	Sudden passenger arrivals or departures	Conference centres, auditoriums, stadium-related facilities

An up-peak calculation is useful for particular planning situations, but it does not represent every operating condition.

For example, a hotel may have passengers travelling between guest floors, reception, restaurants, meeting rooms, and parking. A hospital may require patient beds, wheelchairs, staff, visitors, and service traffic to share or use different vertical transportation systems.

For more complex cases, simulation can model passenger arrival and destination distributions more realistically. CIBSE Guide D 2025 includes separate guidance on calculation-based and simulation-based lift traffic design.

CIBSE

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5. Factors Affecting Lift Selection

5.1 Building population

The expected number of occupants is a fundamental input to traffic analysis.

Population estimates should reflect the building’s intended use, occupancy assumptions, floor areas, and applicable planning requirements. Gross floor area should not automatically be treated as occupied usable area.

A preliminary population estimate may use:

\[ U=\frac{A_n}{a_p} \]

Where:

• \(U\) = estimated population.
• \(A_n\) = relevant net occupiable floor area.
• \(a_p\) = assumed net area per person.

The assumed area per person must be appropriate to the building use and the method being applied. It should not be selected as a universal value for every project.

For mixed-use developments, separate population estimates should be prepared for different occupancies before evaluating their combined or interacting traffic.

5.2 Number of floors and building height

The number of floors served affects travel distance, potential stops, and the time required to complete a trip.

Tall buildings may require higher speeds, zoning, express lifts, sky lobbies, or other arrangements. However, greater speed alone cannot solve every traffic problem.

Architects should coordinate:

• Floor-to-floor heights.
• Total rise and travel distance.
• Number of floors served by each lift.
• Transfer levels.
• Basement and podium connections.
• Roof-level or special-use destinations.

5.3 Rated load and passenger capacity

Rated load is the maximum load specified for the lift under its applicable design and safety requirements.

Rated passenger capacity and the number of passengers assumed in traffic calculations are not necessarily identical. Traffic calculations may use an assumed average loading factor to represent typical operation.

The selected car must also accommodate the intended users and equipment, including wheelchair users, stretchers, hospital beds, luggage, or goods where relevant.

A hospital bed lift, for example, requires a suitable car and door arrangement, not simply a passenger count.

5.4 Rated speed

Rated speed influences travel time, but the relationship between speed and overall system performance is not linear in every practical situation.

A lift spends time accelerating, decelerating, stopping, operating its doors, and transferring passengers. In low-rise buildings with frequent stops, these factors can reduce the benefit of a higher rated speed.

Higher speed may be more important for long travel distances, but it should be evaluated together with:

• Total rise.
• Stop frequency.
• Door performance.
• Passenger capacity.
• Number of lifts.
• Traffic control.
• Energy use and equipment cost.

5.5 Number of lift cars

Adding lifts can reduce the calculated interval and increase group handling capacity, assuming the other parameters and operating assumptions remain appropriate.

However, additional lifts require more shaft space, can increase construction and maintenance costs, and may reduce the area available for occupied rooms.

The correct number is therefore a result of performance analysis and architectural coordination, not a fixed rule based only on the number of storeys.

5.6 Door opening and passenger transfer time

Door operation and passenger movement contribute to total service time.

Door dwell time, entrance width, passenger distribution, and lobby congestion can influence how efficiently people enter and leave the car.

A congested or poorly designed lift lobby may compromise usability even when the calculated traffic performance is satisfactory.

6. How to Select Lifts for a Building: Step-by-Step Method

Step 1 — Define the building

Establish the building use, floor count, floor-to-floor heights, entrance levels, occupancy, and expected future changes.

Step 2 — Estimate passenger demand

Determine the relevant population and identify the busiest periods and destinations. Keep assumptions documented.

Step 3 — Set performance criteria

Define the handling-capacity requirement, interval, waiting-time objectives, and other project-specific service criteria.

Step 4 — Compare lift configurations

Test alternative car counts, rated loads, speeds, door arrangements, and floor-servicing strategies.

Step 5 — Validate performance

Use an appropriate calculation method and commission specialist simulation where traffic complexity or project risk warrants it.

Step 6 — Coordinate the design

Finalize the lift core, lobby, structural openings, pit, headroom, electrical provisions, accessibility, and fire-safety requirements with the relevant consultants.

6.1 Worked example: Preliminary handling capacity and interval

Consider a hypothetical building with the following assumed parameters:

Parameter	Illustrative value
Relevant building population	600 people
Number of lifts	4
Assumed average passenger load per trip	10 people
Assumed round-trip time	120 seconds
Analysis period	5 minutes

The simplified theoretical handling capacity is:

\[ HC=\frac{300\times10\times4}{120}=100 \]

The theoretical handling capacity is 100 passengers per five minutes.

As a percentage of the assumed population:

\[ HC\%=\frac{100}{600}\times100=16.7\% \]

The simplified interval is:

\[ I=\frac{120}{4}=30\text{ seconds} \]

These calculations illustrate the relationships among passenger load, round-trip time, number of lifts, and interval.

Interpretation: The result does not prove that four lifts are sufficient for the hypothetical building. The passenger load and RTT have been assumed rather than derived from a complete traffic model, and the result has not been checked against a building-specific performance criterion.

A real design should establish the relevant demand profile, calculate the round-trip characteristics using the selected method, check the required handling capacity and interval, and examine other important traffic conditions. Simulation may be appropriate where the assumptions of a simplified calculation do not represent the building adequately.

7. Lift Selection According to Building Type

Building type	Key traffic considerations	Architectural priorities
Residential building	Morning and evening peaks, mixed-direction travel	Comfortable access, efficient core, accessible circulation
Office building	Strong up-peak and down-peak demand, lunch peaks	Lift-group efficiency, lobby capacity, zoning in taller buildings
Hotel	Guest movements, luggage, service operations, event peaks	Separation of guest and service circulation where appropriate
Hospital	Patients, beds, wheelchairs, visitors, staff and supplies	Bed-compatible cars where required, accessible routes, clinical/service logistics
Shopping centre	Interfloor movement, concentrated weekend or event demand	Integration with escalators, atria, parking and accessible routes
Mixed-use development	Different occupancies and interacting demand profiles	Zoning, access control, separation of incompatible traffic, core coordination
Industrial or logistics building	Goods movement, equipment dimensions, operational loads	Suitable goods-lift capacity, loading access, service circulation

These are planning considerations, not prescribed lift quantities or universal performance targets. Final selection depends on the building brief, applicable requirements, and specialist analysis.

8. Types of Lifts and Their Applications

Lift traffic analysis helps determine the performance required from the system, while equipment selection determines which type of lift is suitable for the task.

Lift type	Typical application	Selection considerations
Passenger lift	Offices, apartments, hotels and public buildings	Population, capacity, speed, accessibility, and traffic control
Goods lift	Transporting goods and equipment	Rated load, car dimensions, loading method and durability
Hospital or bed lift	Hospitals and healthcare facilities	Bed and trolley dimensions, clear door opening, operational needs
Service lift	Staff, supplies and building operations	Service routes, security, loading, and operational separation
Machine-room-less (MRL) lift	Projects with appropriate space and equipment constraints	Manufacturer-specific spatial requirements, access and maintenance
Observation lift	Buildings where the journey is part of the visitor experience	Visibility, integration with the architecture, and operating conditions

An MRL lift describes an equipment arrangement, not a guarantee of suitability for every building. Likewise, a goods or service lift may need to be considered separately from passenger traffic calculations.

9. Architectural Planning and Lift-Core Design

Lift selection has direct consequences for the building’s spatial organization.

9.1 Lift shaft location

The lift core should be positioned to provide logical access from entrance areas and principal circulation routes.

For many buildings, a centralized core can shorten travel distances and support efficient planning. However, a single centralized core is not necessarily optimal for every building form, especially where the plan is elongated, the building is very tall, or different occupancies require separate access.

9.2 Lift lobby design

The lobby must provide adequate space for people to wait, approach doors, circulate, and move away after exiting.

Architects should assess:

• Clear circulation widths.
• Door swing and adjacent circulation conflicts.
• Wheelchair turning and manoeuvring.
• Potential queues during peak periods.
• Connections with stairs and escape routes.
• Access to reception, corridors, and other principal destinations.

A lobby should not rely on its visual dimensions alone. Its capacity and circulation should be considered against the expected passenger demand.

9.3 Structural coordination

Lift wells, pits, overhead clearances, and support requirements must be coordinated with the structural design.

The architectural team should establish the required core zone early, while the lift manufacturer and structural consultant confirm the equipment-specific dimensions and loading requirements.

Check the following:

• Lift-well dimensions.
• Pit depth and waterproofing provisions.
• Headroom and overhead clearance.
• Machine-room requirements, where applicable.
• Door openings and landing interfaces.
• Structural support arrangements.
• Maintenance and rescue access.

Do not freeze shaft dimensions using generic online tables. Requirements vary with the selected equipment, rated capacity, speed, configuration, and applicable regulations.

9.4 MEP coordination

Lift installation requires coordinated electrical and building-services provisions.

The design team should confirm:

• Power supply and protective devices.
• Emergency communication and applicable backup arrangements.
• Machine-space ventilation or environmental requirements where applicable.
• Fire-alarm and building-management interfaces.
• Earthing and electrical safety provisions.
• Equipment access, maintenance clearances, and installation routes.
• Coordination with sprinklers, ducts, pipes, and cable routes around the lift well.

Specific requirements must be confirmed against the applicable code and approved lift manufacturer’s drawings.

9.5 Accessibility and safety

Passenger lift planning should consider the needs of people with reduced mobility and other users who may require additional manoeuvring space or assistance.

The applicable provisions may address car and door dimensions, controls, signage, communication, access routes, and emergency operation.

Lift planning must also be coordinated with fire and life-safety requirements. Ordinary passenger lifts should not automatically be assumed suitable for firefighting, evacuation, or emergency use.

For Indian projects, NBC 2016 includes provisions addressing lift installation, safety, planning, performance, and building-specific requirements. Applicable state lift legislation, local development regulations, and authority requirements must also be checked.

Bureau of Indian Standards

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10. Lift Zoning in High-Rise Buildings

In taller buildings, one lift group serving every floor may result in long journeys and inefficient use of the available capacity.

Zoning divides the building into groups of floors served by different lifts. For example, one group may serve lower floors while another serves upper floors.

Potential benefits include:

• Fewer intermediate stops for some passengers.
• More efficient handling of particular traffic patterns.
• Better integration with sky lobbies or transfer levels where appropriate.
• More flexible planning of tall building cores.

However, zoning introduces trade-offs. Passengers may need to transfer between lift groups, and the design must account for transfer time, lobby congestion, accessibility, emergency arrangements, and the additional space required.

Zoning should therefore be evaluated through traffic analysis rather than adopted solely because a building is tall.

11. Advantages of Lift Traffic Analysis

• Improved passenger service: Helps assess whether the proposed installation can meet defined demand and waiting-time objectives.
• Better space planning: Supports decisions about lift quantity, car capacity, zoning, and core configuration.
• Cost control: Helps avoid unnecessary equipment or undersized installations.
• Design coordination: Establishes the spatial and performance requirements early enough to coordinate architecture, structure, and MEP.
• Informed comparison: Makes it easier to compare alternative lift arrangements using consistent assumptions.
• Future planning: Encourages consideration of changing occupancy, tenant arrangements, and operational needs.

12. Limitations and Challenges

Lift traffic analysis is only as reliable as its inputs and assumptions.

Potential challenges include:

• Inaccurate building population estimates.
• Unrealistic assumptions about passenger loading.
• Incomplete information about peak traffic.
• Changes to the building layout after the analysis.
• Failure to consider mixed-direction or special-purpose traffic.
• Differences between assumed and actual door performance.
• Lift outages, maintenance, or unusual operating conditions.
• Over-reliance on a single calculated metric.

Calculation methods can be useful for preliminary selection, but complex projects may require simulation and specialist review. ISO 8100-32 explicitly addresses both calculation and simulation approaches within its scope.

ISO

13. Common Mistakes in Lift Selection

Mistake 1: Selecting lifts only by building height

Height is important, but population, demand profile, floor usage, car capacity, and traffic distribution also affect performance.

Mistake 2: Treating rated capacity as handling capacity

Rated capacity describes the load the lift is designed to carry. Handling capacity describes passenger throughput under specified traffic assumptions.

Mistake 3: Assuming a shorter interval guarantees a short wait

Interval is one indicator of service. Passenger arrival patterns and lift control also affect actual waiting time.

Mistake 4: Using the same assumptions for every building type

Residential buildings, offices, hospitals, and hotels have different occupancy patterns and operational needs.

Mistake 5: Finalizing the shaft before selecting the equipment

Generic shaft dimensions may not accommodate the selected car, doors, counterweight, rails, and other equipment requirements.

Mistake 6: Ignoring the lobby and surrounding circulation

A technically adequate lift group may still produce poor user experience if queues obstruct corridors or accessible routes.

Mistake 7: Treating preliminary calculations as final approval

Traffic calculations do not replace equipment design, statutory compliance, structural coordination, manufacturer confirmation, or required safety approvals.

14. Information Architects Should Provide to a Lift Consultant

The following checklist is useful when preparing a preliminary design brief.

[ ] Building type and occupancy schedule
[ ] Floor plans and floor-to-floor heights
[ ] Number of floors and total travel distance
[ ] Estimated population by floor and occupancy
[ ] Basement, podium, entrance and transfer levels
[ ] Expected peak and special traffic conditions
[ ] Required passenger, goods, service or bed-lift functions
[ ] Preliminary core layout and available shaft zones
[ ] Accessibility and operational requirements
[ ] Applicable local regulations and fire-safety requirements
[ ] Future expansion or change-of-use assumptions
[ ] Preferred performance criteria and project constraints

15. Practical Recommendations for Architects

For a reliable lift-selection process:

1. Reserve a provisional lift-core zone during concept planning.
2. Prepare realistic occupancy and population estimates.
3. Identify peak traffic periods and special operational requirements.
4. Set performance criteria before comparing equipment options.
5. Request documented calculations and assumptions from the lift consultant.
6. Use simulation when the building configuration or traffic pattern requires more detailed evaluation.
7. Coordinate the selected equipment with architectural, structural, electrical, fire-safety, and accessibility requirements.
8. Review the lift installation again when major changes occur to the floor plans, occupancy, or building use.

The architectural objective is to integrate vertical transportation into the building rather than treat it as an isolated equipment package.

16. Conclusion

Lift traffic analysis and selection are essential parts of multistorey building design. A suitable lift system must balance passenger demand, handling capacity, round-trip time, interval, car capacity, speed, accessibility, spatial constraints, and operational requirements.

Architects play an important role by providing accurate building information, reserving appropriate space, coordinating the core and lobby, and ensuring that equipment selection supports the overall design intent.

For preliminary planning, calculation methods help compare possible configurations. For complex traffic conditions, simulation and specialist review provide a more detailed basis for decision-making.

The most effective approach is to begin lift planning early, document the assumptions, use appropriate technical guidance, and verify the final installation against the applicable regulations and manufacturer requirements.