In 1979, a minor mechanical fault at the Three Mile Island nuclear power plant triggered one of the most serious nuclear incidents in US history.

A single relief valve became stuck open, allowing large amounts of coolant to escape the system. But inside the control room, operators had no idea what was happening. The indicator light on their console showed the valve’s signal — not its actual position. To the operators, the valve appeared to be closed.

As alarms blared and operators were bombarded with conflicting readings, they responded in accordance with what the system was telling them — and unknowingly made the situation worse. It wasn’t a failure of competence or training. It was a failure of design.

The control system was built around the technology, not the people running it. Multiple similar alarms went off at once, displays were cluttered and confusing, and critical information was buried among the noise.

The official investigation later concluded that poor human factors design — not just mechanical faults — had played a major role in the event.

It’s a reminder that even the most advanced systems can fail if they don’t work for the people who use them.

So… how do you design systems that actually work for humans?

You use an EHFA to drive your HF integration (HFI) process. Championed by Human Factors (HF) specialists, early incorporation of user feedback promotes the users’ voice as integral in design, gaining valuable buy-in from end-users and avoiding costly redesigns later. Added bonus – it also facilitates safety and increases efficiency.

So, what’s an EHFA, then? 

An early HF analysis, or EHFA, is a structured method for assessing how design changes could affect end-users and their ability to do their work safely. EHFA helps you spot risks early and allows you to adjust the design before problems are inherent. When combined with active HFI, it saves your project time and money.

How to apply an EHFA to drive your HF Integration framework

You don’t have to be designing control rooms for nuclear reactors for early human factors analysis to be necessary. Even relatively simple projects can benefit.

For example, we recently supported a maintenance facility upgrade that introduced a fixed roof access platform to replace a mobile gantry. In theory, it was a relatively straightforward change, but in practice could have a significant impact on the maintenance staff and their operations.

So, while the platform was technically sound, I wanted to ensure that the change would truly support the needs of end-users and avoid unintended HF risks. To do this I followed this five-step process:

Step 1: Understand the change 

The existing design was compared with the proposed design to identify:

• What was new
• If the changes impacted how work is done
• The processes that workers must follow
• The tools that are used.

Step 2: Workshop the impact

A task review was conducted during a workshop with key maintenance staff, managers and drivers to validate our findings. While doing this, staff were asked if:

• Roles and responsibilities could change?
• New tasks were introduced?
• The process and movement of critical items were impacted?
• The change introduced new risks?

Step 3: Analyse end-user feedback 

By learning how work is done in real life and understating the limitations of human capabilities, it was discovered that while the platform improved access, it also created unfamiliar tasks and processes. Using HF principles and methods we flagged risks the design hadn’t anticipated, such as access to critical train components, illumination for precise tasks and interlocking risks for interfacing sub-systems.

Step 4: Provide recommendations 

The findings and proposed design changes were documented: fall protection with access gates at critical points, improved lighting, and updated procedures to fit the revised workflow.

Step 5: Develop your HF plan 

Where risks and issues were identified, we used these to develop our HFI framework which could combine future HF analysis to facilitate safety and increases efficiency.

The outcome

Applying the EHFA process allowed us to influence the design before finalisation. Involving staff in the process, built trust and ensured their needs were heard and considered.

Human-centred systems

If you’re designing or upgrading assets and infrastructure, ask yourself: Have you thought about how the changes impact the people who use it?

We’d love to hear your thoughts. Have you used human factors in your designs? What worked? What didn’t? Share your experience or reach out to learn how we can help you design with people in mind.

Profile: David Goble | Senior Human Factors Consultant 

Related Content: Modelling the Human Factor into the Design Process