---
title: Five principles to help you think like a human factors professional
url: "https://www.systra.com/uk/expert_insights/five-principles-to-help-you-think-like-a-human-factors-professional/"
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date_published: 2025-08-11
date_modified: 2025-08-19
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---

# Five principles to help you think like a human factors professional

![Five principles to help you think like a human factors professional](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/featured-image-five-principles-to-help-you-think-like-a-human-factors-professional.png)

**This article presents five principles to help you think more like a human factors professional when involved in the design of new equipment. The principles are based on experience from SYSTRA colleagues of practicing human factors in high hazard industries.**

Whilst we would always advocate the involvement of human factors professionals,
particularly for complex and safety critical projects, our hope is these simple
principles can help you ask the right questions, apply some basic principles,
and help you to identify when you need to call in an expert.

This article will use a made-up project example of a customer help point to
illustrate different methods and the benefits of applying each principle.
Customer help points, like those typically found at train stations, are used to
provide customers with service information and can be used in an emergency.
Pressing the buttons will connect a customer with the appropriate person, or
provide an automated response. We must stress we’ve not worked on this project,
merely picked it as an example.

![figure-1-example-project-customer-help-point](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/figure-1-example-project-customer-help-point.jpg)

_Figure 1: Example project, customer help point_

### 1\. Understand your users

Start by identifying all the users of your new equipment. In Human Factors we
refer to this as “defining the target user population”. The users will vary from
project to project, so identifying who they are at the outset will help you make
informed decisions to suit their needs.

Consumer facing products, such as our customer help point, need to cater for a
wide range of potential users (including different ages, shapes and sizes,
strengths etc). However, for products in specialist domains your target user
population may be different. Perhaps there are job selection criteria that
define minimum and maximums. 

An example of this is train drivers, who have minimum requirements for visual
acuity, for obvious reasons. Here are a few tips that will help you to ensure
your product or system is fit for purpose and adequately considers the
capabilities and limitations of your users. 

Consider the physical attributes of users: When considering the physical
attributes of a user, human factors specialists most frequently employ a design
philosophy, wherein the design is developed to account for the extreme users of
the target population. This is most commonly defined as the 5th percentile
female and the 95th percentile male (this can be for any piece of anthropometric
data of interest, such as stature, reach, of weight). 

Due to the normal distribution of key physical and cognitive attributes across a
sample population, if you demonstrate that the design is suitable for these
extreme users, you in turn demonstrate its suitability for the wider population.
This concept is illustrated in Figure 2, which provides an illustration of the
normal distributions of female and male stature. 

![Graphic for 5 principles insight - Graphic for 5 principles insight](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/figure-2-example-normal-distribution-for-female-and-male-stature-canva-version.jpg)

_Figure 2: Example normal distribution for female and male stature_

Consider cognitive and behavioural attributes: Personas are a powerful tool to
consider the capabilities and goals of your target users.

Personas are a user-centred design approach most commonly used in user
experience design, though increasingly used within the rail industry,
particularly in station design. A persona is a fictional character representing
a major user from your target audience. The personas will describe the users’
needs, experiences, behaviours and goals. 

The use of personas helps maintain focus on end-user needs throughout the design
process. In the case of our customer help point, the personas should include a
wide range of potential users, including passengers or reduced ability and
mobility. A point discuss further below. 

Consider inclusive design: Wherever possible apply inclusive design principles,
this is often called “Design for all” or “Universal Design”. Inclusive design
seeks to accommodate the widest possible range of potential users by not unduly
excluding users of different abilities. 

Readers are encouraged to use the
[Inclusive Design Toolkit](https://www.inclusivedesigntoolkit.com/) developed by
Cambridge University^(1). Figure 3 from the afore mentioned website illustrates
the diversity across the population, and the target population for inclusive
design. 

![figure-3-target-for-inclusive-design-canva-version](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/figure-3-target-for-inclusive-design-canva-version.jpg)

_Figure 3: Target for inclusive design_

The Toolkit provides the following categories for capabilities; vision, hearing,
thinking, reach and dexterity, and mobility. The demands your product or system
imposes can result in difficulty, frustration, or even exclusion of a much
larger group of users than you probably realise. Why not use their
[free exclusion calculator](https://calc.inclusivedesigntoolkit.com/) to see how
many potential users you may be excluding.

At this point you may be saying ‘inclusive design sounds great – however we do
not have the budget or need on our project’. In many cases the huge increase in
potential customers is a compelling argument. Though it should also be noted
that application of inclusive design principles will benefit all potential
users, not just those with reduced ability.

### 2\. Think about the tasks

Make sure you identify all user tasks relevant to your new piece of equipment. A
Task Analysis (TA) is one of the corner stones of human factors engineering. It
is a technique we routinely employ to provide a step-by-step description of the
goals, tasks, and sub-tasks associated with a product or system. 

A task analysis can take many different forms, it is not always necessary to
define each sub-task in detail. As a minimum, designers should define a list of
tasks associated with their product. 

Where a certain task is critical to the success of your product this list can
then be used to derive design requirements. It can also be used as a checklist
to evaluate design options, or as a more detailed evaluation of your preferred
solution. 

The TA can also be used as the basis for subsequent analyses, such as Human
Error Identification (HEI) or Risk Based Training Needs Analysis (RBTNA). Error
identification is discussed in more detail in principle 4. 

Figure 4 provides an example of a Hierarchical Task Analysis (HTA), for our
customer help point. An alternative example is provided in Table 1, which
displays the same information in the format of a Tabular Task Analysis (TTA). 

A key advantage of the Tabular form is the ability to add additional columns to
capture information about a specific sub-task. This may include any equipment
used, the information needs (i.e. what a user needs to complete this step), or
task relevant contextual information (explored further in principle 3). 

![Graphic for 5 principles insight - Graphic for 5 principles insight](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/figure-4-example-hta-for-getting-rail-service-information-from-customer-help-point-canva-version.jpg)

_Figure 4: Example HTA for getting rail service information from customer help point_

![Graphic for 5 principles insight - Graphic for 5 principles insight](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/table-1-example-tta-for-getting-rail-service-information-from-customer-help-point-canva-version.jpg)

_Table 1: Example TTA for getting rail service information from customer help point_

### 3\. Understand the context and consider the overall system

It is critical you consider the context in which the tasks will be performed.
This is one of the key areas of focus for HF professionals, but why is it so
important? The wider workspace and physical environment have a big impact on how
users interact with your product, for instance:

- If your product is designed to be used outdoors then the physical environment,
  including the weather, could have a big impact. For our customer help point
  the physical environment will affect where we position the unit, we must
  ensure there is sufficient room to access and operate the help point. It also
  requires us to consider the impact of rain and sun (glare) on task performance
  and design. 
- The thermal environment can also be a factor. Cold environments will affect
  dexterity and strength, whilst heat will affect vigilance and endurance.
- Finally, the sonic environment can have a big impact on task performance and
  wellbeing. This is a phenomenon well understood by anyone who has struggled to
  maintain focus in a noisy open plan office. In the case of customer help
  point, the location and design of the unit will have an impact on our ability
  to communicate with an advisor in what can be a noisy environment.

Considering this larger system and overall context of use will help you make
better-informed design decisions and avoid costly, or even dangerous mistakes.
In principle 2 we explored human interaction with a system, now we must
recognise this interaction does not take place in a vacuum. 

This concept is well illustrated in the ‘onion’ model. The model includes the
wider context and the various layers of influence. The users, their tasks, and
the equipment (your product) form the core of the model. The inner layers of the
onion represent tangible impacts on a user or system and tend to be well
understood. However, the outer layers are more likely to be overlooked. 

As you work your way outward there are additional influences (ranging from
financial, technical, legal and social) that can have a huge impact of the
success or failure of your product.

![figure-5-onion-model-adapted-from-wilson-and-corlett-canva-version](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/figure-5-onion-model-adapted-from-wilson-and-corlett-canva-version.jpg)

_Figure 5: ’Onion’ model, adapted from Wilson and Corlett2_

Readers are encouraged to identify these external factors – in some instances
they may represent latent failures which can have a huge impact. In the case of
our customer help point, a simple example could relate to maintenance. 

External influences could mean maintenance is limited in time, equipment, and
competence, and therefore ease of maintenance should be a key requirement of
your design. 

### 4\. Think about the errors that people might make

In high hazard industries, a detailed analysis of potential human errors is an
activity best led by a human factors professional. However, in your role as a
project engineer, project manager, subject matter expert, or end-user, you are
fundamental to this process.

All engineering projects will include some form of hazard identification. This
may include Safety in Design (SiD), Preliminary Hazard Analysis (PHA), Hazard &
Operability Analysis (HAZOP), Hazard Identification studies (HAZID), or many
other similar techniques. 

These qualitative assessment techniques each seek to identify hazards, along
with existing and proposed controls. In the absence of a dedicated Human Errors
Identification (HEI) work package, these forums provide the best opportunity to
identify and mitigate potential human errors. 

Experience shows that consideration of potential human errors within these
safety-led techniques is dependent upon the experience of the workshop
facilitator, and the guidewords / prompts they use in the session. 

Furthermore, where users are considered, the hazards typically relate to
workplace health and safety – think trips, slips and falls. Whilst inclusion of
these is important, focussing on these alone will likely omit much more serious
human errors with more severe consequences. As a starting point we would suggest
the inclusion of human factors related guidewords in whichever hazard
identification technique you choose to use – two examples are provided below.

One option is to use an error taxonomy based on Reason’s model^(3) of human
error types. The error types are further categorised using Rasmussen’s Skill,
Rule, and Knowledge model^(4) which provides insights to the human behaviour and
decision making leading to the human error.

![figure-6-reason-and-rasmussen-model-of-human-error](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/figure-6-reason-and-rasmussen-model-of-human-error.jpg)

_Figure 6: Reason and Rasmussen model of human error5_

Referring back to our customer help point example. A preferred HEI technique is
the Systematic Human Error Reduction and Prediction Approach (SHERPA).
Completing a SHERPA analysis at the design stage would help you identify
potential errors that could be expensive to rectify or have adverse consequences
on system performance. An example SHERPA analysis is provided below, building on
the Task Analysis presented in principle 2.

![Graphic for 5 principles insight - Graphic for 5 principles insight](https://www.systra.com/uk/wp-content/uploads/sites/11/2025/08/table-2-example-extract-of-sherpa-analysis-canva-version.jpg)

_Table 2: Example extract of SHERPA analysis_

### 5\. Consider the physical demands of your product

Of course, any ‘top 5 principles’ had to include something about physical
ergonomics – perhaps the topic people most frequently associated with the human
factors discipline. We’ve included this as the final principle as successful
application is dependent upon two afore mentioned principles, namely:
understanding your users, and thinking about the tasks they will perform. 

Physical ergonomics assessments seek to achieve the best possible ‘fit’ between
a product and its users. This can have many positive results, including: 

-  Increased productivity
-  Improved ease of use
- Eliminate or minimise risk of injury

In the case of our customer help point, accessibility standards mandate the
height of the unit. Compliance with any applicable standards is obviously the
starting point, however there are other physical ergonomics considerations that
you should be aware of. These considerations will be informed by your task
analysis, or task list from principle 2. 

In New South Wales, Australia, the Assets Standards Authority (ASA) stipulate
that “Help points shall be positioned within a height range of 700mm and 1250mm
so that the user is able to access the functional components of the help point
unit”.

This range has been defined to ensure wheelchair users can operate the help
point however this is likely to be below the optimum working height for our
tallest potential users, here defined as a 95th percentile male. 

A 95th percentile Australian male has a stature of 1898mm and a standing elbow
height of 1219mm (both including a 25mm footwear adjustment). Therefore, if
placed at the lower end of the range, a taller male will be required to bend to
view the help point display and to operate the controls, microphone, and
speaker. 

This is where we make use of the considerations from the task analysis, such as
task frequency, task length etc., as using a help point is a very infrequent
task and the duration of use is short, these non-optimum postures would still be
considered acceptable, even for a 95th percentile male. 

This example illustrates how anthropometric data can be used in combination with
your tasks to assess a design. If a poor fit between your product and user has
the potential to cause injury, or inability to use your product, you should
create design requirements to address the mismatch and optimise the solution for
the widest range of users.

#### Find out more

If you would like to know more about the human factors services on offer with
SYSTRA ANZ
[visit their page here](https://www.systra.com/australia/services/operational-integration/human-factors/)
. Information on human factors expertise at SYSTRA in the UK & Ireland
[can be found here](https://www.systra.com/uk/services/systems-approach/our-approach-to-human-factors/)
. 

#### References

1\. [Inclusive Design Toolkit](https://www.inclusivedesigntoolkit.com/)
developed by Cambridge University

2\. Wilson, J & Corlett, N, Evaluation of human work, Taylor & Francis, Second
Edition, 1991

3\. Reason, J. Human Error, Cambridge University Press, 1990

4\. Rasmussen, J. Human errors: a taxonomy for describing human malfunction in
industrial situations, J. Occupational Accidents, pp. 311 – 333, Vol. 4, 1982

5\.
[Human error in plant maintenance, 2018](https://www.maintenanceandengineering.com/2018/04/06/human-error-in-plant-maintenance/)

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