Experts checking the Tube and buses for Covid-19 have found no evidence of the virus.
Imperial College has been carrying out monthly tests on London transport for coronavirus in the air and in common areas touched by passengers.
The testing, done on behalf of TfL, used machines able to draw in 300 litres of air every minute to check air quality on public transport and in stations.
Swabs were also taken from ticket machines, barriers and hand rails, and no Covid-19 was found.
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Lilli Matson, TfL’s chief health, safety and environment officer, said: ‘The range of measures in place across London’s transport network to ensure it is cleaner and safer than ever is huge.
‘We have been using hospital-grade cleaning fluids, installed hand sanitiser points across the network and changed cleaning schedules to ensure that stations are cleaned even more regularly.
‘We want to reassure customers who need to use the network that we are doing everything we can to keep the network safe, and this testing will help ensure we continue to do so.’
The results are used to ensure regular cleaning with anti-viral fluid of areas considered ‘of greater risk’.
Testing was carried out in Waterloo and Euston stations and on the Northern line and on selected bus routes, the same in previous months.
Professor Sir Roy Anderson, an epidemiologist at Imperial College, who was not involved in the research, said that in general ‘surface contact is not the main issue’ for the transmission of Covid-19.
He told the Evening Standard: ‘The main issue is our behaviour as individuals and groups. Outdoors, the likelihood of transmission is much less than in enclosed spaces. These particles are airborne. That is the bit that is most important.
‘Contaminated surfaces, of course you have got to pay attention to. My own view is that it is more aerosol-related transmission – inhaling those droplets or micro-droplets.’
TfL commissioner Andy Byford previously urged Londoners to return to the network.
‘We are ready when you are ready. The system is safe. We encourage people to use it,’ he added.
TfL says it will continue with monthly tests to ensure it is doing all it can to keep staff and customers safe.
The news comes as a four-week national lockdown starts in England, where people are only encouraged to travel if it is essential.
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