Design for usage: Ease of use

The second element in the ‘design for usage’ stage of the product lifecycle is ease of use.

Users expect all kinds of products to be as easy to use as possible. After all, they should not need to be a wrestling champion in order to operate a lever or push a pedal! Product parts that are in contact with people should be designed to fit the human body and should be comfortable to use. They should not have any negative impact on the individual, even when the products are used for prolonged periods of time.

All engineered products are expected to be easy to use and smooth to operate. Some of the things that should be considered when designing for easy usage include the ease with which a user can operate mechanical actuators, such as levers and pedals. Machines are used by people of all ages and widely variable physical capabilities. Therefore, users expect that mechanical actuators will not require excessive force to operate. Take for example early cars: the pedals, levers and the steering wheel of these cars were directly connected to the mechanical parts they controlled with wires or rods. As a result, they required considerable muscular power to operate. This made early cars quite difficult to drive for many people. Today, the steering wheel and almost all levers and pedals in a car are assisted by hydraulic or electric motors to make them very light and smooth to operate.

Ergonomics or human factors engineering

The study of the relationship between humans and machines has developed over the years into a discipline of its own, known as ergonomics or human factors engineering. In ergonomics, engineers design machines that are easy to use, comfortable, and don’t cause any negative impact on the health of individuals, even when the machines are used for long periods of time.

Some examples

• Car seats are designed so that they perfectly cradle the human body and provide comfortable and healthy support to all body parts. They should also provide the same level of support for all kinds of people, big and small.
• Computer monitors: designers must make sure that the brightness and contrast of computer monitors can be adjusted to suit the visual requirements of different people. All monitors should also provide adequate resolution and image sharpness to reduce fatigue to the human eye.
• The size and labelling on the buttons of a machine are also considered during the design process to make sure that they are fit for purpose and can be seen and used by all the people.
• In software engineering design, user interfaces should be designed to be clear, obvious, and accessible.
• One of the most important ergonomic factors is the noise level emitted by machines. Clearly, users prefer machines that produce low levels of noise. But market competitiveness is not the only downside. Products that don’t meet certain limits on noise level will be in breach of the law. For example, in the UK, the external noise produced by a passenger car cannot exceed 72 decibels. The decibel is a unit commonly used to measure the intensity of sound.

Next steps

In this step, we examined some of the factors that affect the usability of a product. We have given some examples, but there are many other factors that we did not mention and you are encouraged to reflect on the usage phase of a product,

There is, of course, a relationship between ease of use and safety. A product that is not easy and comfortable to use may eventually endanger the health of users. In the next step, we will consider the safety and reliability of products and the third element in designing for usage.