London double decker buses will be restricted to a maximum 20 passengers from Saturday when TfL reopens its front doors and starts charging fares again.
Single-decker buses, depending on the size of the bus, will carry between six and 10 customers. TFL said the driver will have discretion to allow more customers on board if they are travelling in households or groups.
As well as limiting the amount of passengers who can board buses at any given time, London's buses will also be returning to front-door boarding again.
Customers will be required to touch in with their Osyter, contactless and concessionary cards.
The move follows collaborative work by University College London and Unite union in assessing the risk for cab drivers and bus operators.
Analysis by UCL has found that the steps TFL have taken - by adding a film layer to screens, and sealing off gaps around the screen - substantially reduces the risk to drivers of contracting the virus from customers.
From Saturday 30 May, passengers will start to see signage on 124 bus routes instructing them to board using the front door.
It is anticipated that all London buses will return to front-door boarding by mid-June.
TFL said that reverting to pre-pandemic arrangements will encourage traditional flows on and off the bus and will help improve social distancing for customers entering or exiting the bus.
The new limits of only carrying 20 customers on double-decker busses will help customers to maintain two-metre distance between them and others wherever possible.
Heidi Alexander, Deputy Mayor for Transport, said: “The safety of our transport workers and passengers is absolutely paramount.
“Working closely with unions, TfL has introduced a range of measures to improve safety including putting in place an enhanced anti-viral cleaning regime across the network, applying a protective film to the Perspex screen of bus driver cabs to seal off holes and preventing passengers sitting next to bus drivers. All frontline staff have also been offered simple face masks."
She said, scientific advice "confirms that is safe for front door boarding to resume on buses" and will be rolled out across the network on a route-by-route basis.
But she said the message is still "please work from home and travel on foot or bike if you can."
If you do absolutely have to travel on the network "wear a face mask, avoid the busiest times and respect the new protocols put in place," she added.