The drivers worked on locomotives on the Heart of Wales line
Three train drivers who claimed that an industrial injury left their hands permanently disabled have been awarded more than £22,000 in compensation.
They contracted Carpal Tunnel Syndrome (CTS), which can be caused by pressure on a nerve in the wrist, while working for Arriva Trains Wales in Carmarthen.
The company said it was looking at what steps to take with advisers on legal matters, and on health and safety.
Aslef said the Swansea Crown Court case sets a precedent for all train drivers.
Thompsons Solicitors, representing Aslef, said the judge delivered his judgement after a five-day trial, he found all three drivers suffered from CTS and that it was work-related.
According to Thompsons, the judge also said Arriva Trains Wales had failed to assess the drivers' working conditions for risks to health and safety, or to put preventative measures in place.
One of the three Arriva Trains Wales drivers affected was Paul Studholme, 43, who said in a statement issued through Thompsons that the condition forced him to take more than 10 months off work.
He discovered he was suffering from the condition in 2004 and said: "It is a great relief that the judge has supported our argument.
"CTS forced me to go on the sick for a number of months and as a result I became depressed.
"The fact that three of us in the same depot all developed this condition shows that more should have been done to improve our working conditions."
The three drivers were among 50 working at the depot driving locomotives along the Heart of Wales lines.
After they were diagnosed the drivers contacted Aslef which then instructed the solicitors to purse a claim for compensation.
Aslef said it argued that the symptoms of CTS were caused by the drivers' repetitive work, adopting awkward wrist postures and operating brake and power controls in cramped conditions.
'Deserve our praise'
The members had complained of inadequate seats with little or no adjustment and no arm rests.
After the judgement was delivered, Aslef general secretary Keith Norman said: "This is a fantastic result for our members and sets a precedent for all train drivers across the country who suffer from CTS.
"These three drivers deserve our praise for sticking with this case and I'm proud of all the union's local and regional officials for persisting with it.
"Employers should ensure they put proper risk assessments in place to make sure all rail workers have the safest conditions possible".
Arriva Trains Wales issued a statement saying: "Following today's judgement we will be taking the time to consider the implications of the decision and the next steps with our legal and health and safety advisers".