As a sign of the easing of coronavirus travel restrictions in England, train companies will increase the number of services on offer as of Monday.
The Rail Delivery Group said services would be increased from about 50% of the standard timetable to 70%.
Passengers are being urged to avoid non-essential travel while the trains shall be operating at 10% capacity in a bid to ensure social distancing.
British Transport Police will have more officers at London stations in a bid to control crowds.
Will Rogers, the managing director at East Midlands Railway, said the new timetable “will only allow a small rise in the number of passengers we can accommodate”.
“We urge everyone to only go by train if it is necessary and keep public transport for key workers and those who must travel,” he added.
Passengers travelling by train are being asked to wear a face covering and keep a 2-metre distance from other people where possible. Transport operators are being urged by the government to rearrange, remove or limit seating “to try and ensure social distancing is observed”.
Only London North Eastern Railway ticket holders who also have a reservation will be permitted aboard trains. Passengers are asked to sit in a window seat, limited to one person per row of four seats with a minimum of two empty rows between each passenger.
However, those travelling as a household will be allowed to sit together but must maintain “a safe distance” from other passengers.
Avanti West Coast customers were warned that anyone without a reservation might 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 would be “significantly reduced capacity on each and every one of our trains”.
For weeks, the number of rail services has been reduced as a result of the COVID-19 induced collapse in demand coupled with the resultant rise in staff sickness.
But the government is now urging people in England to go to work if they cannot work from home. Advice in Northern Ireland, Scotland and Wales remains that people should stay at home.
Meanwhile, the Rail, Maritime and Transport union described the increase in train services as a “high-risk strategy” and expressed concern that “rushed political considerations could well override the safety issues for staff and passengers”.
The union has called for compulsory protections for passengers and rail workers, including the enforcement of 2-metre social distancing on trains and the compulsory wearing of face masks by passengers, which should be provided for free at stations and be easy to dispose of safely.
Mick Cash, the RMT general secretary, said, “We are opposed to the early relaxation of lockdown measures and believe that non-essential workers should avoid using trains. When people absolutely must use a train, there should be new compulsory protections.
“We have the crazy situation of Eurostar passengers arriving with masks on into St Pancras but then not wearing masks when they transfer to the tube or other rail services.”
A Department for Transport spokesman said the message remained that people should only go to work if they cannot work from home and they should avoid public transport if possible and maintain social distancing if they have no other choice.