Vertical Transportation Design and Traffic Calculations – Part Two

In the previous article “Vertical Transportation Design and Traffic Calculations – Part One”, we explained the following points:

  1. Applicable Standards and Codes Used In This Course,
  2. The Need for Lifts,
  3. The Efficient Elevator Design Solution
  4. Parts of Elevator System Design Process
  5. Overview of Elevator Design and Supply Chain Process.

 Today we will explain the following points:

  • The Concept of Traffic Planning,
  • Methods of Traffic Design Calculations
  • Principles of Interior Building Circulation.

Sixth: Introduction to Traffic Planning and Design


1- The Concept of Traffic Planning

As a Vertical transportation system designer, the first question you will ask to the client is about The building parameters which are listed in step#2 in article Vertical Transportation Design and Traffic Calculations – Part One”, which were:  

  • Type of users (normal, disable or blind),
  • Building usage (office, residential, hospital…),
  • Number of floors,
  • Floor heights,
  • Net areas for each floor,
  • Building population,
  • Passenger arrival patterns,
  • Car park usage,
  • Location of special floors (meeting floors, restaurants…).

The second question will be what is the status of the building? is it existing or new building? The answer will be used to assign the tools used to estimate the building population of the building to start the traffic / circulation planning as follows:

  • For existing buildings, the traffic of the building population can be surveyed, by observation or by means of an attached data logger, to determine the current activity and traffic pattern.
  • For new buildings, the traffic of the building population can be estimated based on the experience gained with previous similar structures which were tabulated in some codes like in below table:


Building  type

Population estimate


1.5–1.9 persons/room


1.5–1.9 persons/bedroom


3.0 persons/bed space*


0.8–1.2 m2 net area/pupil

Office (multiple tenancy):


10–12 m2 net area/person


15–25 m2 net area/person

Office (single tenancy):


8–10 m2 net area/person


12–20 m2 net area/person

* Patient plus three others (doctors, nurses, porters, etc.).

Table-1 Estimation of population

As a general, The Traffic planning in building projects is dependent on the “traffic analysis” study. We can define the Traffic analysis study as follows:

The Traffic Analysis Study:

It is the study of the population distribution and their predicted pattern of flow within the day.

Therefore, the “traffic analysis” study will vary according to the type of building and its use, and the type of occupier. For example, an office building typically requires more elevators than an apartment building due to heavier loads & traffic.

The traffic analysis study helps in selecting:

  1. The correct number and type of transportation devices;
  2. The right sizes and speeds of the transportation devices;
  3. The proper control systems and features to optimize and synchronize traffic flow;
  4. The optimum layout for the transportation devices and correct positioning in the building and in relation to one another;
  5. Easy access to buildings and a smooth flow of people and goods.

In the traffic analysis study, there are two key factors affecting the efficiency of an elevator system:

A- The Quantity of Service:

The quantity of service factor shows how many people will use the lift system over a defined period of time which is represented by the handling capacity.

The Handling Capacity Of Elevator System:

it is the total number of passengers that the system can transport within a certain period of time, (usually 5 minutes i.e. 300 seconds) during the peak traffic conditions (usually the morning up-peak) with a specified average car loading (usually 80% of the rated capacity of the elevator).

If the handling capacity of a lift system is too small, there will be lot of people queuing for the lifts during up peak. Also, the lift cars will have to go more round trips in order to clear off the queue. Thus system with too small handling capacity will degrade the quality of service.

B- The Quality of Service:

The quality of service factor shows how long the passengers must wait for an elevator and represented by passenger waiting time. The shorter the passengers waiting time the better the quality of service.

However, passenger waiting times cannot be easily measured. Some designers, therefore, use the interval of car arrivals at the main terminal as an indication of service quality.

The interval of car arrival of the lift system must be short enough so the handling capacity of the lift system will be suitable to the arrival rate of the passengers at the morning 5 minutes uppeak period.

This means that for efficient lift system design:


The handling capacity of the lift system ≥ the arrival rate at morning 5 minutes uppeak period

Otherwise the design will be non-efficient.


  • The handling capacity of the lift system must not be too high comparing to the arrival rate at morning 5 minutes uppeak period, otherwise the system design will be a wasteful design.
  • The calculation/ estimation of the above two factors; quantity of service “Handling Capacity” and quality of service “Passenger waiting Time or interval of car arrivals” will be explained in next articles.

As a conclusion:

the concept of traffic planning  for sizing lift systems is to match the quality of service (passenger waiting time or arrival rate) with the quantity of service (handling capacity) and get an economic solution based on the above Rule#1.

2- Methods of Traffic Design Calculations

There are (4) methods used for the traffic design and analysis as follows:

First: Calculation methods, which includes:

  • The Formula-Based Method (Classical Method Method),
  • The Monte Carlo Simulation Method.

Second: Simulation methods, which includes:

  • Discrete Event Simulation Method,
  • Time Slice Simulation Method.

1- The Formula-Based Method (Classical Method)

The formula-based method is based on formulas used to size the lift system to serve the demands of a building’s occupants by matching the demands for transportation with the handling capacity of the installed lift system for the worst 5-minute period during the morning uppeak traffic condition to get an economic solution.  The Formula-Based Method will not be used for some special conditions like:

  1. the case of multiple entrances to the building (rather than a single entrance),
  2. the case where the top speed is not attained within one floor jump (or even two or three floor jumps),
  3. the case of unequal floor heights,
  4. The case of unequal floor population,
  5. The case of combinations of above special conditions.

2- The Monte Carlo Simulation Method

The Monte Carlo simulation is a practical means to calculate the round trip time for an elevator during the up-peak (incoming) traffic conditions, under a combination of any or all of the above special conditions (not solved by the Formula-Based Method) such as multiple entrances, top speed not attained within one or more floor journeys, unequal floor heights and unequal floor populations.

The block diagram of the Monte Carlo Simulation method for the calculation of the round trip time of the elevator during up peak conditions is shown in Fig.1. It comprises the following main blocks:

  1. The random scenario parameter generator.
  2. The kinematics calculator.
  3. The round trip time calculator.

In addition a master module controls the three blocks above to run each block and produce the final result and interface with the user.

Fig.1: Block diagram of the Monte Carlo Simulation round trip time tool

3&4 - The Simulation methods

They are based on analysis of a discrete digital simulation of the building, its lifts and the passenger dynamics with the other major conditions (down peak, inter-floor and two-way). These methods greatly reduces the possibility of errors compared to the formula-based method and can handle more complex design cases.


In this course, we will explain only the first method which is The Formula-Based Method (Classical Method).


Important Notes for Traffic Planning by using The Formula-Based Method (Classical Method)

  • The traffic analysis and design calculation in this course is mainly relevant to commercial office buildings.
  • The conventional procedure used in the traffic design of lift systems is to determine the handling capacity for the uppeak traffic situation and compare it with the arrival rate as mentioned before in Rule#1 in above.
  • The traffic period for evaluation when sizing an office building is usually a morning up-peak, 5-minute segment. During this period of time, little or no traffic is moving interfloor or down in the building. The lifts are loading passengers at the main lobby, distributing those passengers to various upper floors and then making an express trip back to the main lobby for the next load. Therefore, studies are based upon “one-way traffic” in the up direction with no stops at the intervening floors in the down direction. It is possible to consider some down travelling passengers, but there is no consensus as to how big this flow should be. uppeak traffic flow is the best method which can be used to compare any designers results.
  • In general, if the uppeak traffic pattern is sized correctly all other traffic patterns will also be adequately served. There are exceptions to this comment. For example: in hotels at meal times; in hospitals at visiting times; in buildings with trading floors (insurance and stock markets), which open at specified times and at lunch time in all buildings.
  • Many of the recommendations are based on empirical data acquired by observation and the experience gained in their application.
  • It is important to remember that the distribution and size of the population of any large building changes regularly. Thus a design which is tightly planned may prove inadequate once a building has been occupied for a year or two. To understand the effect of these changes on a design, it is essential to document the criteria and decisions taken at all stages of a design.
  • It is important that the architect or planner establishes the lift system required at a very early stage and not after the rest of the building has been designed, as has often happened in the past.
  • The Formula-Based Method will not be used for some special conditions like:

  1. the case of multiple entrances to the building (rather than a single entrance),
  2. the case where the top speed is not attained within one floor jump (or even two or three floor jumps),
  3. the case of unequal floor heights,
  4. The case of unequal floor population,
  5. The case of combinations of above special conditions.


From above explanation, the key parameters in traffic analysis study are as follows :

  1. Handling Capacity,
  2. Passenger Waiting Time,
  3. Arrival Rate,
  4. No. Population,
  5. Interval Of Car Arrival.

To design the best handling capacity of any lift or escalator system, we must start with a consideration of the traffic flows “circulation” through the building. Circulation is defined by Dober, 1969 as the act of passing from place to place.

Building circulation, both horizontal and vertical, is the lifeblood of any building, and hence if a successful building is to be designed it is essential that the architect take expert advice at conception at early stage of the project.

3- Principles of Interior Building Circulation

The study of the circulation of people in the interior of buildings is very important because it affects the ability of the transportation system to receive and dispatch the passengers efficiently and effectively. The study of Interior Circulation is based on many principles which the designer must be familiar with them, these principles are:

  1. Efficiency of Interior Circulation,
  2. Human Factors,
  3. Circulation and Handling Capacity Factors,
  4. Location and Arrangement of Transportation Facilities.

First: Efficiency of Interior Circulation

The efficiency of interior circulation inside the buildings is affected by many factors like:

  1. Movement Mode,
  2. Movement Type,
  3. Human Behavior,
  4. Building Shape and Its Interior Design.

1- Movement Mode:

People will generally moving horizontally inside their place of work. Then, they may change their mode of movement from horizontal to vertical, in order to reach a higher or lower level. To do this they will use stairs, moving walks and ramps (passenger conveyors), escalators or lifts.


2- Movement Type:

People will move naturally inside the place without the help of any mechanical equipment (moving walks and passenger conveyors, escalators or lifts), but when using moving walks and ramps (passenger conveyors), escalators or lifts, their movement will be mechanically assisted.


People are generally referred to as pedestrians when moving on foot and as passengers when mechanically transported.


3- Human Behavior:
The movement of people around a building is a complex movement because each one has:

  • Different concepts of route,
  • Different purposes for moving,
  • Different levels of urgency,
  • Different characteristics of age, gender, culture, handicaps; etc.

So, there is unpredictability in humans behavior reflects to unpredictability in their movement inside the buildings.


4- Building Shape and Its Interior Design:

For example, both tall/slender and low/squat buildings are inefficient while The ideal shape is “compact”. The circulation efficiency is affected by some factors related to the interior design of the building like:

  • The relative location of rooms,
  • The relationship of major spaces with entrances and mechanical elements,
  • The importance of the journey undertaken,
  • The separation of different traffic types,
  • The need to group some spaces together,
  • The conflict of vertical and horizontal circulation modes,
  • The design and location of portals (i.e. entrances, doorways, gates etc.), corridors, stairs and mechanical transportation systems (moving walkways, moving ramps, escalators, lifts).

So, interior design of the building must be coordinated to ensure:

  • Free flow of people, goods and vehicles,
  • Minimal wastage of space,
  • Prevention of bottlenecks.


  • It is important to size each facility Thus the handling capacities of corridors which lead to stairs or lifts should be adequate for their anticipated traffic load.
  • The interior design may be affected by other regulations such as fire and safety codes and these must be taken into account. Design planning recommendations are given for lifts in Section four of BS 5655: Part 6 and ISO 4190-6W.


Requirements of Efficient Interior Circulation in a Building

The well-designed interior circulation in a building must fulfill the following points:

  • To consider all circulation routes: These include principal and secondary circulation areas, escape routes, service routes and waiting areas.
  • To provide clear and obvious routes: Pedestrians should be able to see the route to take, perhaps assisted by good color coded signs and open view.
  • To ensure that the circulation patterns are logical: An example is the avoidance of pedestrians passing through a lift lobby, where other persons are waiting.
  • To ensure that incompatible types of circulation do not coincide: An example is pushing goods trolleys across a pedestrian mall in a shopping center or sterile/non-sterile movements in a hospital.
  • To minimize the movement of people and goods: Related or associated activities will be grouped together in same area, e.g.: sales and marketing; personnel and training; etc. in an office building.

In the next article, we will continue explaining other Principles of Interior Building Circulation. Please, keep following.

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