Selection that stands up: Why validated assessment tools are essential in safety-critical recruitment

Dr Stephen Fletcher, Joint CEO and Occupational Psychologist at the OPC, explains why it’s crucial to back up decisions with solid evidence when recruiting for safety-critical roles.

What is validation in recruitment, and why is it important?

At its core, validation is a scientific process. When we talk about validation in recruitment, we’re asking one fundamental question: do our assessment tools e.g. psychometric tests, structured interviews or whole recruitment processes, accurately predict individuals more likely to perform well and work safely? In the rail industry, with so many safety-critical roles, having evidence behind our recruitment decisions isn’t optional; it’s essential.

In high-risk environments like rail or engineering, selecting the right person isn’t just a matter of efficiency, it’s about safety. Validated tools give us confidence that we’re identifying individuals less likely to make critical errors. That insight helps support a strong safety culture, assists in reducing operational risk, and can help protect lives.

Psychology is a science, and occupational psychologists are committed to using evidence-based methods. Validation is a core part of that commitment. Without it, we risk making decisions based on assumptions or untested beliefs, instead of data.

What does a validation study involve?

Validation studies help us test whether our recruitment tools actually work. For example, if we’re hiring signallers, we begin by reviewing the selection process. This might include concentration or rules-based tests, e.g. the RAAT, or interviews and a group exercise. We gather applicants’ assessment scores and, for successful candidates, collect performance data like training outcomes, supervisor or NTS ratings, and safety metrics such as incidents or near-miss reports.

The real value comes when we analyse the relationship between the two data sets to identify meaningful statistical correlations. Do higher scores at selection predict better or safer job performance? If so, we’re confirming the tools help us make effective decisions, validating the recruitment process (not the person) and ensuring we’re measuring what matters most.

For reliable results, we typically need data from at least one hundred individuals, although some OPC studies have involved many more. Using advanced statistical methods, we look for clear links, giving us confidence we’re selecting candidates more likely to succeed and contribute to a safer, more effective railway.

Why it matters

Validation helps us focus on the tools that genuinely predict job success, whether ability tests, structured interviews or practical exercises. It also allows us to refine recruitment processes, perhaps adjusting the weighting of certain tools, or removing those that add little value. This supports more accurate hiring decisions, especially where safety is critical.

And who benefits?

Validation can bring value to both organisations and candidates. For employers it can help improve recruitment accuracy, potentially reduce training failure rates, save costs and possibly enhance operational performance through more effective teams. For candidates, it can mean a clearer and condensed selection process, a better fit between people and their roles, and a stronger chance of long-term success and well-being in their job.

Validation also strengthens legal and regulatory defensibility. If a recruitment decision was to be challenged or a new employee is involved in an incident, it can help demonstrate that the process was fair, consistent, and fit for purpose.

Lessons from other sectors

Over the past three decades, we’ve conducted validation studies across rail, aviation and customer service sectors. One airline believed all their best call centre agents were extroverted and empathic. However, our study revealed their top performers were actually more self-focused and goal-driven. These kinds of insights can help clients to rework and improve their attraction strategy alongside their selection processes. In rail, we’ve completed many UK and international studies of train driver selection processes, alongside other role validations. We’ve also validated tools for track workers as part of a major project with the Health and Safety Executive (HSE). This research showed specific psychometric tools could accurately predict safe and effective performance. Insights that were later shared as industry best practice by the HSE.

A powerful tool for continuous improvement

Validation doesn’t just tell us what works. It also reveals what doesn’t. It helps sharpen recruitment processes, provides focus on what truly matters, and ensures each stage adds measurable value and stands up to scrutiny. Ultimately, it can support fair, evidence-based decisions that support better hires, safer teams, and stronger long-term performance.

If you think the OPC can add value to your recruitment processes through validation, contact the friendly team today.

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