Commuters should face away from each other when they cannot stay two metres apart under new coronavirus rules, the government has said.
The government has urged those who cannot work from home to return to their workplaces from Wednesday, but transport unions have called the plan “dangerous” for passengers.
In its new guidance on how to travel safely during the coronavirus outbreak, the government told passengers to minimise the time they spend near other people and avoid physical contact with them.
However, the government accepted that “there may be situations where you can't keep a suitable distance from people”, such as on busier train or bus services or at peak times.
"In these cases you should avoid physical contact, try to face away from other people,” it said.
The document added: "The risk of infection increases the closer you are to another person with the virus and the amount of time you spend in close contact."
Passengers are advised to "avoid using public transport where possible" and should "instead try to walk, cycle or drive".
People who do travel should be "thinking carefully about the times, routes and ways you travel".
The guidance states that "if you can, wear a face covering if you need to use public transport".
Passengers are also advised that after completing their journey they should wash or sanitise their hands.
Transport operators are being urged to rearrange, remove or limit seating "to try and ensure social distancing is observed".
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This may include blocking off seats in close proximity to others and removing face-to-face seating.
Single users of black cabs and minicabs should sit in the back left-hand seat of cars, according to the guidance.
Last week, transport secretary Grant Shapps announced a £2bn package to increase cycling and walking capacity across the UK.
This would include pop-up bike lanes, wider pavements and bus-only streets.
On Tuesday, he said: "Transport operators and staff have been working hard to ensure that people who need to get to work are able to do so, including crucial NHS workers and all those on the front line of the fight against the virus.
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"Alongside the cycling and walking revolution we are launching, and clear guidance to passengers and operators published today, we can all play our part by following the advice and reducing pressure on public transport.
"If we take these steps, all those who need to use public transport should feel confident that they can do so safely, with the space to maintain social distancing as far as possible."
But the National Union of Rail, Maritime and Transport Workers (RMT) criticised the government’s plans.
Its general secretary, Mick Cash, said on Tuesday: "The government’s ‘return to work’ policy from Wednesday morning risks unleashing total chaos on a transport network which has not been told to prepare for a rise in numbers until next Monday.
“This is a ridiculous and dangerous way to treat both staff and passengers alike and will have potentially lethal consequences.
“Maintaining social distancing on trains and tube is a massive logistical exercise that requires planning, resources and the protection of staff managing the flows of passengers. To rush that exercise is a disgrace.”