Commuters are being told they can “travel with confidence” as rail services were ramped up on Monday.
Industry body the Rail Delivery Group (RDG) insisted trains are “safe to travel in” as timetables were increased to around 90% of pre-coronavirus pandemic levels.
This means additional and longer trains on many routes, particularly at peak times.
RDG director of nations and regions Robert Nisbet told BBC Radio 4’s Today programme: “Today is really about telling commuters that ‘you can travel with confidence’, that we are going to be putting on more trains to increase capacity.
“But also what we’re doing is ensuring that those trains are safe to travel in by increasing hygiene (and) cleaning in stations and on trains.
“Obviously we’re also asking people to do their bit as well, by wearing face masks and making sure they keep their hands clean before and after they travel.”
Rail punctuality has improved during the pandemic with 83% of stops at stations made within a minute of the schedule in July, compared with 66% in July 2019.
Anthony Smith, chief executive of passenger watchdog Transport Focus, said the industry must “focus on maintaining good performance”.
He warned: “Disruption and any crowding from this will be especially unwelcome and has the potential to damage trust in the railway.”
Timetables were slashed in March as the virus led to a reduction in available railway workers and demand for travel, but were gradually increased to around 80% before being ramped up on Monday.
Mr Nisbet said there are “important learnings” for the industry in terms of the impact on performance of running a full timetable.
“Before Covid, one train was leaving a station every second,” he explained. “We were congested.
“What this (pandemic) has allowed us to do is to look at the timetable and its resilience, and to see where we can improve and increase punctuality, and build and maintain that as we now build back up the timetable.”
Southeastern is providing an extra 900 carriages on its weekday services, restoring timetables to 98% of normal levels.
LNER has added 10 extra Anglo-Scottish services to its daily timetables.
ScotRail increased services last month ahead of lessons resuming at Scottish schools.
Department for Transport figures show train demand across Britain is at around 30% of pre-pandemic levels.
A survey of 2,000 public transport users by Transport Focus conducted last month suggested that 77% of train passengers were satisfied with the ability to keep a safe distance from others.
The research also indicated that 50% were satisfied with the ease of finding out how busy a train service would be before travelling, and 69% were satisfied with the number of people wearing face coverings.
Some operators are returning to normal refund rules on Monday after restrictions were eased due to the pandemic.
This means season ticket refunds will no longer be backdated up to 56 days from the last date of travel, and admin fees of up to £10 may return for refunds of single or return tickets.