Govia Thameslink Railway has said it has just finished retreating its 20,000th train with a long-lasting viricide.
It says the viricide can kill coronavirus for weeks at a time.
If the treated 105,000 carriages were placed end to end, Govia Thameslink says they would stretch 2,100km, from London to Iceland.
With numbers of COVID-19 cases increasing in recent times, the train operator hopes continued application will provide passengers with added confidence about returning to rail.
Working throughout the pandemic, the viricide has been applied to all 2,700 carriages in the Great Northern, Southern, Gatwick Express and Thameslink fleet and they are regularly re-treated to keep them that way. GTR has also treated its 235 stations over 7,000 times.
Trains that are air-conditioned also refresh the air on board every six to nine minutes.
Steve Lammin, engineering director at Govia Thameslink Railway, said: “We’ve been working relentlessly to protect passengers from Covid during the pandemic with our long-lasting viricides. Now, as more and more people return to the workplace, they can do so knowing this work continues, allowing them to travel with confidence.”