Back on track

Buildings would be demolished, and new towers would creep towards the sky in their place. Snow flurries would be followed by spring growth, green foliage would be replaced by autumn leaves.

While the railway has also transformed over the course of his career – an ebb and flow of new logos, management and technology –the train drivers themselves remain largely constant. In an age where new graduates expect to enter a variety of roles during their careers, train driving is seen by many as a job for life.

That is until one day in 2016, Friend failed a colour vision test as part of a periodic medical. Friend, who had worked as a train driver for 16 years, could no longer work in a safety-critical operational role.

“I had never had a colour vision-related incident when driving in the daytime, nighttime, snow and fog,” he shared with OT.

Then a year later, Stephen Pritchard also failed the colour vision test as part of a periodic medical and was moved off operational duties.

While Pritchard had always been aware that he had an issue with his colour vision, receiving the news that he could no longer drive trains came as a blow.

“I knew it was coming, but it was still devastating when it hit,” he said.

This failed test would set in motion a chain of events that would see Pritchard tirelessly campaign for a change to the railway’s colour vision standards.

Over the course of eight years, he would comb the internet for all he could find about industry colour vision standards. He would collaborate with a leading academic, Dr Marisa Carmona Rodriguez,who had already spearheaded a new way of approaching colour vision for pilots, electricians, air traffic controllers and coastguards.

Finally, in 2025, he would receive the news that the Rail Safety and Standards Board was introducing a new two-stage colour vision test – a test that both Pritchard and Friend were likely to pass.

“I’m looking forward to getting back,” Pritchard shared.

A constant fear

When Pritchard was growing up, he would hear stories of the railway from his father who worked as a train guard.

He has memories of train drivers who were friends with his father letting him ride in the front cab.

“I had always envisaged joining the railway. I thought I would follow in my father’s footsteps,” Pritchard said.

He started work as a train guard in Kent in 1999 before moving to the North East in 2007. In 2014, Pritchard joined Southern Railway to complete his driver training.

While Pritchard had repeatedly passed the Ishihara test while working on the railway, he shared that there were inconsistencies in how the test was conducted.

There is variation in lighting levels and how long candidates are shown the plate for. Pritchard said that sometimes people would be given a second opportunity to see the correct number.

“When you look again, you can see the correct digit, but it is not as prominent as the incorrect digit,” he said.

“In some of the medicals, I had the examiner actually trace the number out for me,” Pritchard added.

When Pritchard failed his periodic medical in 2017, he was only able to work in non-operational roles.

This took a significant personal toll on Pritchard who worried that the associated pay cut would mean he would have to move house and change his daughter’s school.

The news that the colour vision standards would change provided Pritchard with a sense of hope.

“The perennial threat of my job hanging by a thread is gone,” he said.

Asked why he persevered in his efforts over the course of eight years, Pritchard said that his stubbornness prevented him from walking away from the railway.

“There was a sense of injustice that, through no fault of my own, I was being removed from a job that I can safely do,” he said.

“At the beginning my mental health took a really bad turn, but after a while I realised that it was the rough and tumble of the process. No negative thing is necessarily the end of the day, because I had been through them before,” Pritchard observed.

He paid tribute to the support of Andy Cook – a train driver with normal colour vision who was a union health and safety representative at the time.

“I had a vested interest in the outcome of this, but he didn’t, and he put in as much work as me,” Pritchard said.

You may be born with colour vision deficiency, but that doesn’t define your dreams

At a crossroads

As a teenager, Chris Friend travelled from his home in Morden to Paddington before boarding an intercity 125 and watching the scenery flash by.

“I went as far as I could on a return ticket for a pound and come back in time for tea,” he said.

Friend grew up around trains. His family worked on the underground and his father was a train spotter.

Although his salary had dropped by half after he was moved off the driver grade, Friend took a philosophical approach to the upheaval in his career.

As an onboard supervisor, he could look out at the expanse of the ocean and the rows of ships docked at Southampton and Portsmouth.

OT

Chris Friend, onboard supervisor

Friend missed the problem solving of being a train driver – the times he would have to think on his feet to safely convey passengers to their destination.

But he was still on the same trains, travelling the same routes, helping people from inside the carriage rather than behind the wheel.

“I was still on the railway, so that was half the problem out of the way,” he said.

“You think it is what it is. What else can you do?” Friend shared.

Cook, who has worked as a train driver for 22 years, was motivated to support changes to the railway colour vision standards after observing the experience of his colleague, Friend.

Cook explained that Friend was facing the end of his career on the railway before he secured his role as an onboard supervisor.

“I was in my car in the car park and saw Chris in his civvies going in for his last day,” he said.

“Chris couldn’t find another role within the company. Here was someone who was absolutely committed to the railway and losing his job – that really upset me,” Cook emphasised.

Cook shared that one of his primary concerns was how inconsistencies in the colour vision test were affecting the safety of the railway.

“If people are able to cheat or lie on the test in order to get a safety-critical job, then that is dangerous,” he said.

Cook views the updated two-stage colour vision test as part of the modernisation of the railway.

“It's bringing our rail industry into 21^st century,” he emphasised.

Describing how vision standards for train drivers have evolved over time, Cook shared that previously train drivers were not permitted to wear varifocal glasses.

“It was only bifocals and before that, in the days of steam trains, you weren’t allowed to wear glasses at all,” he said.

Historical methods for assessing the colour vision of train drivers included identifying a series of coloured lights and an exercise where drivers were asked to arrange pieces of dyed wool in the colour of the rainbow.

Asked why he took a stand when he was not personally affected by the issue, Cook reflects on the example of his grandmother who worked in the munitions factory after the second world war and would stand up to management on behalf of her colleagues.

“We need to make sure that people are treated fairly,” he emphasised.

Pushing for change

When Dr Marisa Rodriguez Carmona stepped up to the stage at a Leeds train driver union conference in 2019, Pritchard recalled looking back at the delegates from the front of the room and observing how her presentation had transfixed a room of close to 100 train drivers.

Rodriguez Carmona explained the complexities of colour vision to the delegates who then voted on a motion to campaign for changes to the colour vision standard.

“They voted for the motion unanimously,” Pritchard said.

Reflecting on why the members would vote for a motion that affected a relatively small number of train drivers, Pritchard described the close ties that form on the railway.

“The depot is just a hive of people talking to each other. The friendships and bonds you get on the railway are much stronger than any other workplace I've worked in,” he said.

There were times in the process where it looked unlikely that Pritchard would meet the proposed new standard.

“It would still have been an amazing achievement just to get some people back in the job,” he reflected.

The change that ASLEF campaigned for – to introduce a CAD test as a secondary test for train drivers who fail the Ishihara test – was eventually rolled out in March 2025.

Rodriguez Carmona, who developed the Colour Assessment and Diagnosis test as part of her PhD at City St George's, University of London, highlighted that the new testing process provides a fairer assessment for people with mild colour vision deficiencies, while also enhancing safety.

“The main improvement of using the CAD test is not only allowing more people to pass, but also knowing their level of colour vision,” Rodriguez Carmona shared.

She highlighted that there can be misconceptions about how significant a colour vision deficiency is for someone’s daily life.

“People often think colour blindness means you just see in black and white, which isn’t really the case,” Rodriguez Carmona said.

"But colour vision deficiency isn’t one-size-fits-all — it varies from person to person, ranging from almost normal vision to more severe cases,"she said.

Friend only realised that his colour vision was different to others when his father pointed out a shape in an Ishihara-style poster at an airshow that he could not see, while as a child Pritchard overheard his mum telling a friend that he had failed a colour vision test.

“My colour vision deficiency is very mild. I may have difficulty picking out shades of colour in a paint matching range, but otherwise it has never been an issue,” he said.

The CAD test is a display-based assessment that changes the saturation of the stimulus depending on whether or not the test subject can see it.

OT

Dr Marisa Rodriguez Carmona, senior lecturer in optics, City St George's, University of London

For each industry, the required level is set according to the safety-critical tasks that rely on colour vision in that vocation.

Within aviation, Rodriguez Carmona interviewed pilots about tasks within their roles that rely on colour vision.

“We also travelled London to Edinburgh, back and forth in a day, looking at what pilots looked at in the cockpit and outside,” she said.

Rodriguez Carmona and her team developed a simulator that replicates precision approach path indicator (PAPI ) lights — red and white signal lights that help guide pilots when Instrument Landing System is not available.

They fine-tuned the simulator with meticulous accuracy, using real airfield lights and adjusting their intensity to reflect conditions like dust in the air.

“We had evidence-based research on the actual physical tasks in aviation that rely on the use of colour,” she shared.

Testing with this simulator helped researchers decide which level to set the pass/fail threshold on the CAD test.

There was a sense of injustice that, through no fault of my own, I was being removed from a job that I can safely do

In the next phase of the railway research, scientists will carry out experimental work to determine what level of colour deficiency is needed for colour-abnormal subjects to perform colour-related tasks safely with the same accuracy as colour-normal train drivers.

“The biggest challenge will be to come up with a picture of what is the most safety critical colour-related scenario,” Rodriguez Carmona said.

Through her work in aviation, Rodriguez Carmona was able to deliver life-changing news to teenagers who had previously been told that their chosen vocation was not possible.

Her research established that around 35% of colour deficient applicants could be certified as safe to fly.

“We would see these teenage boys who had wanted to be pilots all their life and we were able to tell them ‘You can now become a pilot’,” she said.

“You may be born with colour vision deficiency, but that doesn’t define your dreams.”