We recommend conducting user requirements analysis as early as possible, usually as part of the project requirements specification stage.
This is because the user requirements provide the foundation for the design and development of a product or system that meets the needs and goals of its target audience.
By conducting user requirements analysis early on, designers and engineers can gather insights into the motivations, preferences, and limitations of the customer base they are designing for. This can include factors such as cognitive abilities, physical capabilities, communication preferences, and work habits. Understanding these factors can help designers create products that are easy and intuitive to use, efficient, and safe.
In practice, it can be done later, when it’s realised that human factors input is needed.