New research from the Rail Safety and Standards Board (RSSB) will help more people with colour vision deficiency (colour blindness) work in safety critical railway roles, such as train driving.

Being able to see and distinguish colours is an important requirement for safety-critical roles on the railway, with the Ishihara test commonly used to check for colour vision deficiency. The Ishihara test works by presenting a series of coloured plates with numbers or patterns hidden within a field of dots, and identifies colour-deficient vision - but not the degree of colour vision loss. This means people with minor colour vision loss could fail the test even though they are able to safely perform the role.

ASLEF, the trade union representing train drivers, asked RSSB to research colour vision testing as they were concerned some drivers were being removed from duties, having failed the Ishihara test on a minor colour vision deficiency that did not impact their ability to safely perform their role.

RSSB’s research has identified a new two-step approach to colour vision assessment. The Ishihara test remains the primary screening test, with 100% correct answers needed to pass. Any applicants who fail then take a more detailed Colour Assessment and Diagnosis (CAD) test to determine the specific degree of their colour vision deficiency. RSSB’s analysis shows this new approach could allow approximately 47% of people currently failing the Ishihara test to be assessed as safe to perform the role. 

Luisa Moisio, RSSB’s Director of Research said:

“For years, people with minor colour blindness have not been able to work in safety critical jobs on the railway. This could be discriminatory, breaching equality law, by preventing capable people from being considered for employment.

“Our research has identified a more thorough testing process to establish if someone with colour blindness can safely perform a role. We are now changing medical Standards to implement this new fairer testing system, giving more people an opportunity to join the railway family.”