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Although the word 'ergonomics' has entered the popular vocabulary, many do not know precisely what it means. Cars are advertised as being 'ergonomically designed', as is pretty much any hand tool with a peculiarly-curved handle. Ergonomics is, in fact, a wide-ranging discipline which can be applied in many areas of design, engineering and daily work.
What is Ergonomics?
Ergonomics1 is the application of scientific information concerning humans to the design of objects, systems and environment for human use. Its role in the design process is to look out for the interests of 'end users' and to ensure that designs meet their needs.
Readers will be familiar with many everyday irritations such as:
- Why can only tall people reach things from the top shelf at the supermarket?
- Why does my mouse make my wrist ache?
- Why can't I work out how to set my video?
- How do I get my wheelchair onto this bus?
- Why do none of the options on the call centre menu seem to apply to me?
- Why does my head touch the roof of this car?
- Why can't they make the print bigger in these product instructions?
- Where's the on/off switch on this thing?
- How on earth do I find out how to use this website?
Broadly, ergonomics addresses the following issues:
Safety. Are these railings high enough to stop someone falling over them? Will repeatedly lifting this widget onto a conveyor belt hurt someone's back? Will the control room operator notice the alarm indicator for imminent nuclear meltdown?
Effectiveness. Will this wheelbarrow allow me to shift more concrete? Will shoppers on my e-commerce site be able to find what they want? Can I launch my surface-to-air missile in sufficient time to intercept the incoming enemy fire?
User Experience. Is this kitchen knife a joy to use? Is finding interesting books on this site such a breeze that I'll come back time and time again? Do I enjoy the comfort and efficiency of my work environment so much that I can hardly keep away from it?
In practice, of course, these aspects tend to be interrelated — for example, an Air Traffic Control system which allows the controller to identify and avert potential conflicts effectively is safer for the passengers and less stressful for the controller.
The ergonomics approach uses information from psychology (cognitive, behavioural, perceptual, social, organisational), anatomy and physiology to address these issues. It can be applied to something as small as a pair of tweezers or as large as an aircraft carrier.
Fitting Equipment To People
The role of human sciences in ergonomics is to provide designers and engineers with information about human characteristics which they can use to ensure that their products 'fit' their users. However, unlike in 'pure' engineering, where one can specify a hole size for a standard screw, the 'one size fits all' approach does not always work for the many and varied members of the human species. Information is required on the variability within the human population
To take a simple example, imagine you are a manufacturer of beds. You know how to make a bed just the right size for you. But you are only 5'2" tall, and you know for a fact that there are taller people out there — your business partner, for example, is a towering 5'9" — and you don't want to exclude them from your potential market, nor to insist on a customer-deterring Procrustean2 solution. So how do you satisfy everyone? Well, you might find out that the tallest person in the UK is Mr Hussain Bissad at 7'7". The only problem is that beds that length wouldn't fit in many bedrooms. So where to draw the line? Well, as it happens, ergonomists have, over many years, compiled collections of anthropometric data — various dimensions measured from a sample of the population. Statistical methods allow us to use these to infer the proportion of the population that would fit a bed of given size. One might decide, therefore, to build a bed long enough for 98% of the population and supply the other 2% as special orders3.
The general aim of ergonomics is to accommodate as much of the population as is appropriate. It is almost never useful to design for an 'average' person, because this person will, by definition, be taller than 50% of the population, but shorter than the other 50%: designing for the average may exclude half of all people. Collections of anthropometric data — which give measurements for all sorts of human parts such as stature, arm length, head circumference, armpit height, hip-knee length etc — typically state means, standard deviations and values for the 5th to 95th percentiles4. It is quite common to design for the 5th percentile to 95th percentile range — although it should be noted that this excludes 10% of the population. Great care must be taken in deciding how big a proportion of the population to accommodate. For example, one might reasonably suppose that pretty much any woman travelling on public transport late at night should be able to reach an emergency alarm button, so this must be brought into 100% reach.
It is not only in physical dimensions that products have to fit humans. For us to use objects effectively, safely and with pleasure, various human characteristics have to be taken into account, such as:
- The size of text required for readability at a particular distance.
- The number of aircraft an Air Traffic Controller can handle without becoming overloaded.
- The number of choices someone can remember from a spoken list.
- The amount of weight that can be carried safely and comfortably.
- The temperature and humidity that a manual worker can endure without becoming heat stressed.
- The complexity of a computer interface that will still let people find the information they need.
- The forces that will stop children being able to undo the tops of medicine bottles.
- The appropriate names to use for menu items so that they are familiar and meaningful to users.
Identifying The Human Need
The essential characteristic of an ergonomically designed object, system or environment is that it enables people to do the things they need to do. This sounds obvious until you remember all the times that this hasn't worked for you:
- The mobile phone which buries the 'add new name' entry somewhere down amongst the menus.
- The can-opener which won't fit neatly in the cutlery drawer.
- The new DVD player which doesn't work in quite the same way as the old one.
- The call centre which asks you to phone a separate number to get the information you thought they could give you.
- The website whose help pages never quite give you the information you need (mentioning no names...).
The key to these problems is to identify what people want to do and how they want to do it — then design around that. This identification of human needs is central to ergonomics and is supported by a loose set of techniques under the heading task analysis.
Task analysis consists of documenting users' goals and the sequences of tasks and subtasks they perform to achieve them. These sequences may also include alternate ways of doing things, how mistakes are corrected and how to cope with unexpected events. Task analysis can deal with both physical activities (eg, selecting an item on a computer screen) and cognitive (eg, deciding what to select). It also addresses not only the use of the designed object itself, but also tasks in the wider context.
The general aim of task analysis is to provide a way of looking at a design from the end-users' viewpoint. To put it crudely, if an engineer or designer looks after the what of a product, the ergonomist can use task analysis to look after the why5.
While ergonomists can be thought of as the users' advocates in the design process, they will readily admit that they are but second-hand substitutes for the users themselves. In ergonomics, user involvement is regarded as the sine qua non of good design.
An international standard6 has specified the nature of user-centred design. It is aimed at software-based systems, but its principles are equally valid for physical products.
The key is to get future users (or a sample of 'typical' users) involved in a process of 'iterative' design. Iteration — making successive improvements until you get it right — is important because for a new product, users may not know exactly what they want any more than the designers. Take, for example, someone presented with a mobile phone in the early 1980s. How long did it take before people realised they wanted to put them in handbags and that predictive text for a text-messaging system would be useful?
The user-centred design process has the following stages:
Understand the context of use. Specifying the characteristics of the users and the overall tasks they will carry out. This is where task analysis comes in.
Define the user requirements. Specify what the system or product will do and how it will do it.
Produce user-centred designs. Produce initial designs, bringing in human data where necessary.
Involve users in assessing the designs. Designs must always be evaluated to ensure that they do what they are meant to do in a way that the users are happy with. This need not involve testing a fully-working design. Early evaluations can be made with pen and paper, cardboard models, 'working mock-ups' of web pages, etc.
This cycle should continue until a satisfactory design is reached. Although it might seem like extra work, it can bring savings by allowing design faults to be ironed out at the early stages when they are cheaper and quicker to correct.
The outcome of a user-centred design process will be products which are themselves user-centred. They will be based on evolving user requirements, will match human characteristics and will have been judged satisfactory by users.
Ergonomics can bring benefits in many areas relating to work, recreation and everyday living. Its application is increasingly encouraged by government bodies in the UK, US7, Canada, Europe and Australia.
Areas in which ergonomics has become particularly prominent include:
- Web usability.
- Inclusive design (eg, accessibility issues for people with disabilities, including web accessibility).
- Prevention of Work-Related Upper Limb Disorders8.
- Safe and comfortable working with office technology.
- Accident cause and prevention.
- Consumer product design.
- Military systems.
It is difficult to sum up the breadth of ergonomics. Perhaps the best way is to state a general principle:
Humans shouldn't have to adapt to technology. Technology should be built around humans.
The Ergonomics Society (UK-based).
The Human Factors and Ergonomics Society (US-based).
Bad Designs: A scrapbook of illustrated examples of things that are hard to use because they do not follow ergonomics principles.
AnthroKids: an example of a collection of anthropometric data (for US children).
Alertbox: An extremely informative online magazine on usability issues by Human Computer Interface guru, Jakob Nielsen.
Def Stan 00-25: Human Factors for Designers of Systems: The UK Ministry of Defence's comprehensive guidance on ergonomics aspects of systems and equipment. Enter '00-25' in the search box.
Working With VDUs: A leaflet from the UK Health and Safety Executive which gives advice on how to adjust your computer facilities (Adobe® Acrobat format).