Wearing face coverings will be compulsory on public transport in England from 15 June, the transport secretary has said.
Grant Shapps said “every precaution” must be taken as passenger numbers were expected to increase when lockdown measures were eased further.
Coverings must be worn on buses, trams, trains, coaches, aircraft and ferries.
Very young children, disabled people and those with breathing difficulties would be exempt, he said.
It comes as the UK recorded the deaths of another 176 people who tested positive for coronavirus, taking the total number of deaths in the UK to 39,904.
Speaking at the daily coronavirus briefing, Mr Shapps said face coverings would be “a condition of travel” and not wearing one could “ultimately” lead to a fine.
But he added: “Why wouldn’t people want to do the right thing?”
He said surgical masks must be kept for clinical settings and instead travellers should wear the kind of face covering that could be made at home. They should cover the mouth and nose and can be as simple as a scarf or bandanna tied snugly behind the head.
Mr Shapps also stressed that social distancing and regular hand washing were still the most important measures to prevent the disease spreading.
The rule change coincides with the planned reopening of non-essential retail and return of some secondary school pupils in England from 15 June, which Mr Shapps said would put “more pressure” on the public transport network.