Train companies have said they may have to reduce timetables to cope with shortages of staff forced to isolate by the NHS Covid app.
The Rail Delivery Group, which represents train operators, said that as Covid cases were increasing, more staff were being “pinged” by the app.
It said that while companies were working to “minimise any disruption, there may be an impact on services”.
The Department for Transport (DfT) said it had agreed to reduced timetables.
“We recognise the challenges operators are facing due to staff shortages and have agreed that they can consider a reduced or revised timetable in the event of serious shortages,” a DfT spokesperson said.
“These timetables must prioritise safe and reliable services and we urge passengers to check before they travel.”
The number of people in England and Wales being “pinged” by the NHS app rose by 17% to 618,903 alerts in the week to 15 July.
Some rail companies have already announced cancellations because of pinging. Govia Thameslink Railway (GTR), which runs Thameslink and Southern trains, has announced it will introduce a reduced timetable from Monday 26 July.
GTR said: “Unfortunately, like other industries across the country, coronavirus continues to affect our operations. We have fewer colleagues available at the moment due to a significant increase recently in the number of our people affected by Covid-19.
“Our colleagues have continued to work tirelessly throughout the pandemic and we’re really sorry for any inconvenience caused by the latest changes.”