ScotRail has announced new "rules for safer travel" - as it moves to increase the number of services running next month.
The new guidance comes following the launch of the Scottish Government's transport guidance plan.
The operator says it will add a small number of daily services to the timetable from next Monday - offering more options during peak travel times.
But it will still be running at less than half of normal capacity.
The rules from ScotRail are:
1. Do not travel if you feel unwell or have a temperature.
2. Travel away from the main commuting times (0700-0900 and 1600-1830) wherever possible, as trains will be busiest around then. The earliest and latest trains serve key workers, like NHS and care home staff.
3. If you think it's not safe to board a train, don't do it and wait for another service.
4. Wear a face mask or covering and where possible maintain physical distancing.
5. Be patient. You might not be able to board your first choice of train, as physical distancing means most seats need to be left empty.
There will also be floor markings and other signs to set out distancing measures in the largest stations, while some facilities like waiting rooms will be closed.
People are being warned to expect an increase in the amount of time it takes to buy a ticket and board a train - and recommends people buy in advance using the ScotRail app or website.
David Simpson, operations director, said: "We are asking our customers to play a very important role in keeping everyone safe by following the Scottish Government advice to cover their face while travelling.
"The message remains the same: people should only travel when it is essential to do so. We need everyone to take personal responsibility. If you think it's not safe to board a train, don't do it and wait for another service.
"Adding a small number of services will provide key workers and essential travellers with more opportunities to practice physical distancing. We urge people to help us by making safe and sensible decisions."
Professor Jason Leitch, Scotland's national clinical director, said: "Everyone across Scotland's railway is working incredibly hard to provide a service for those people who need to use the train in this difficult time, and we really appreciate everything they are doing.
"Train services are having to operate in a very different way just now, so we are asking people to only travel by train if it is essential, and to follow ScotRail's five rules for travel."