ScotRail has warned passengers to keep face masks on while aboard trains.
The railway operator said many commuters were wearing a face mask at first, but later taking it off during their journey.
ScotRail also said some train routes across the country were seeing just 40% of travellers wearing face masks despite them becoming mandatory on public transport a month ago.
It said around 90% of its customers have complied with the requirement overall since it was brought in on June 22, but it estimates only 60% – and in some cases just 40% – are doing so on some routes.
Syeda Ghufran, ScotRail engineering director, said: “While it’s encouraging to see that most people across the country are following the requirement and covering their face when travelling, we need everyone to take personal responsibility for their travel choices.
“The mandatory wearing of face coverings helps keep you, your fellow customers and our people safe.”
The operator has given away more than 20,000 free face coverings to help people get used to the new normal for rail travel.
It has also now applied face-covering vinyl to two of its Inter7City trains, which operate on routes connecting Scotland’s seven cities, as a way to raise awareness of the rule.
Ms Ghufran added: “By applying a face covering to two of our iconic high-speed Inter7City trains, we hope to help raise more awareness about the mandatory wearing of face coverings on our trains and in our stations.”