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In part one of this blog, we looked at the importance of usability engineering, the necessity of challenging assumptions and an overview of what the regulations ask for.

In part two, we will be looking at the key stages within the usability process and where it sits in your overall product engineering design and development roadmap. But, first of all, let’s start by recapping 10 key benefits of involving users in your product development process from the outset:

  • Helps to identify use issues or design flaws early to prevent expensive redesigns
  • Allows potential use errors to be designed out
  • Device development is based on evidence rather than assumptions about user need
  • Focuses the development team with a clear specification
  • Enhances user experience (ease of use reduces user workload, need for training & reliance on instructions for use)
  • Provides opportunities for innovation, leading to a competitive edge
  • Reduces time to market
  • Increases chance for successful validation, regulatory approvals and market acceptance
  • Reduces the chance of customer complaints, adverse events and device recalls once in use
  • Ultimately delivers a safe, usable, competitive device to end-users


  • Insight & Concept Development
    In this stage, it is important to really get to know and understand your users, their motivations, requirements, the use environment and even their capabilities and limitations. This is also when you define the risk and UI specification to ensure that any known issues and critical tasks are identified and written into your programme. The output of this stage is a living document that should evolve with your development as updates are incorporated.
  • Design Implementation & Verification
    The key part of this stage is the evaluation and mitigation of any use risks you have identified in stage one. By moving through prototype phases, results of any formative evaluations can be fed back in the design through iteration.
  • Transfer to Manufacture & Validation
    Finally, the last stage of the process focuses on summative evaluation and the production of the usability engineering documentation. If you can prove that any risks identified in stage one have been assessed and reduced and you can prove that the product is safe and effective to use, by the intended users, in the product’s use environment, then this can be fed into the usability engineering documentation.


The three main stages within a development programme are concept generation, detailed design and development and transfer to manufacture. However, there is more to a programme than these core steps. Other elements happen in parallel, but human factors and usability need to interact constantly. The three usability stages we have already detailed need to align and integrate seamlessly with the main development stages in order to get the best product at the end of the programme.

A large number of product recalls are attributed to poor product design. It is therefore imperative that your user interface is based on actual user needs. By challenging assumptions (you’d be surprised at how even the most confident assumptions can be incorrect!) and integrating user insight into your design throughout, risks can be mitigated from the start. It is important to show your iterative design, illustrating how you have mitigated and controlled risks to an acceptable level before clinical studies.


Traceability is vital within the design and development process. During the insight and concept development phase, you should be conducting primary research to ensure that your user interface specification is based upon actual user needs (as mentioned above). This research forms part of your User Requirement Specification (URS), which in turn is used to define your Product Requirement Specification (PRS), which is derived from the functional & technical requirements of your product. Having this process fully detailed provides full usability traceability from user insight to product validation. We have discussed using the V-Model for development verification and validation in a previous blog, dedicated entirely to URS and PRS, so please check that out here. The V-Model will provide you with a process against which you can verify against your product requirement specification and validate again your user needs, demonstrating that you designed the right product and designed the product right.

Finally, to fully demonstrate safe and effective use, multiple evaluation methods should be employed. There are two core techniques used to evaluate use risk in this process. Use risk analysis aims to capture foreseen risks with low likelihood and user studies aim to capture the unforeseen use risks. There are a variety of different tools and methods which can be used depending on factors such as the phase of development, level of details required, the nature of the UI but together these two techniques are what make the process effective at mitigating use risk.

To read how we employed a fully integrated product development programme, incorporating design, development and usability, please check out this human factors case study.

For further information on how eg technology can support the human factors and usability integration of your product development, please get in touch.

Via email on, by giving us a call on +44 01223 813184, or by clicking here.