Passengers travelling on mainline services from Cumbria and the south of Scotland are being encouraged to wear face coverings and book their journeys in advance.
It comes as rail services increase at the start of the first full working week since Prime Minister Boris Johnson set out his plan for easing the coronavirus lockdown in England.
He urged employees unable to work from home to return to their places of employment.
Britain’s train companies are ramping up their services to meet the demand, with 70% of the standard timetable up and running - it was operating at 50%.
At the moment, only those who cannot work from home should travel to their work place using public transport.
But in a bid to keep passengers and staff safe through social distancing, their capacity will be reduced to as little as 10% of normal levels, and passengers are being urged to avoid non-essential travel.
There is a possibility trains may not stop at later stations if the service becomes busy early on in its route.
Those travelling by train are asked to wear a face covering, to reduce the risk of spreading the virus, and can only board train services with a pre-booked reservation.
Some stations will have a one-way system in place to make sure people are staying two metres apart, in line with Public Health England guidelines.
Avanti West Coast
Avanti West Coast warned its customers that anyone without a reservation may not be able to travel on their choice of train due to capacities being limited to around a quarter of normal levels.
Train operator Northern said there will be “significantly reduced capacity on each and every one of our trains”.
In order to keep passengers and staff safe, the train operator is encouraging users to adhere to their guidance.
In Scotland, ScotRail is continuing to keep trains clear for essential workers only and have developed five safety rules for travellers to follow.
Rail unions say that stricter rules for passengers and more safeguards for rail staff are needed to minimise the risks for everyone.
Craig Johnston, from RMT Union, said: "We've a problem with how it has been done but we have no problem with the increase in services.
"If we are going to increase the number of passengers then the more services the better."
North of the Border, the advice from First Minister Nicola Sturgeon is to avoid all but essential travel.
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