Dozens of stations on the London Underground network could be closed from Thursday following the outbreak of Covid-19.
Up to 40 stations which do not interchange with other lines could be closed, while the Waterloo and City line and Night Tube services will not run from Friday.
Buses in the capital will be reduced and people are being urged “not to use public transport for anything other than essential journeys”.
London Mayor Sadiq Khan said: “People should not be travelling, by any means, unless they really, really have to. Londoners should be avoiding social interaction unless absolutely necessary, and that means they should be avoiding using the transport network unless absolutely necessary.
“London will get through these extraordinarily challenging times, and ensuring the capital’s critical workers can move around the city will be crucial.
“Frontline staff across our health and care service – as well as those ensuring Londoners stay safe and can access food and other essentials – should be commended for their hard work.
“We owe it to them to do whatever we can to help them do their jobs effectively.
“I’m urging Londoners to only use public transport for essential journeys. Everyone should follow this and the other advice to help keep themselves and each other safe.”
TfL said it would also be gradually reducing the frequency of services across the network from Monday, “to provide a service for critical workers to get to where they need to – ensuring that remaining services are not overcrowded”.
London Overground, TfL Rail, the DLR and London Trams will also be running fewer services from next week.
Transport Commissioner Mike Brown said: “The advice from Government is clear – people should now only be making journeys that are absolutely essential. We and our staff are doing everything we can to ensure that people who need to make essential journeys can continue to do so.”
Passengers are being urged to check their journey on the Transport for London site before they travel.