Transport for London (TfL) has seen Tube passenger volumes drop by 92% year-on-year after as of April 2.
Mike Brown MVO, London's transport commissioner, confirmed that passengers numbers have also dropped by 80% on bus services in the capital.
The remaining capacity is in use by key workers, although there has been a reduction of 30% due to drivers, station staff, controllers and maintenance teams not able to come to work, including those self-isolating or ill with coronavirus.
Brown said the training involved with providing cover for these roles takes many months and “it is simply not possible to replace them immediately while maintaining a safe service”.
Five London bus drivers have already died after contracting coronavirus.
Peter Kavanagh, regional secretary at union Unite, said: “Unite has been working continuously with Transport for London (TfL) and the operators to ensure the safety of drivers and others in the industry who are performing a heroic job in getting NHS and care workers to their places of work.
"These measures include deep cleaning of buses, additional cleaning of touch points, the sealing of screens around the driver, the provision of hand sanitizer for all and placing the passenger seating closest to the driver out of bounds."
Unite has been holding daily meeting with TfL to explore further safety improvements and is calling on the government to make provisions for transport workers to wear Personal Protective Equipment (PPE).
TfL and Crossrail construction work has been temporarily paused to reduce the number of construction workers needing to travel into central London.
TfL has sent out around 13 million emails urging customers to stop travelling.
It has also used announcements at key stations and posters translated into 13 languages, and sent out messages on social media and through its website.
TfL is currently processing refunds on season tickets “as quickly as we can” and has waived the usual £5 redemption fee.
Brown added: “My message remains simple: the threat you pose to London when you make an unnecessary journey is real.
“No one should be travelling unless you are a critical worker making an absolutely essential journey. Please don't travel. Help us save lives. Help us protect the NHS.”