A notable feature of London’s virus lockdown has been day after day of clear blue skies. Now that Prime Minister Boris Johnson has asked some Britons to return to work, the city’s mayor is trying to keep it that way. Sadiq Khan said Friday he’ll seek to raise green taxes and promote car-free transportation in a bid to prevent polluting vehicles taking over the city as commuters return to their jobs. Unclean air can create heath risks that could increase the severity of the disease, which may put even greater demands on the National Health Service.

This week, Johnson said people should return to their places of work if they can’t do their jobs from home, and to avoid public transport where they could. That’s presented a dilemma in London where buses and trains are the most popular method of commuting, and cars, vans and trucks are deterred with regulations and charges.

Congestion Charge

Khan has proposed raising the Congestion Charge, a tax drivers pay to enter some central parts of the city, to 15 pounds ($18) from 11.5 pounds. That would be the first increase in six years and the most since it was introduced in 2003. Certain discounts offered to residents and regular users will be eliminated, and it will be extended to include weekend travel. He’s also proposing to turn large swathes of central London into temporary car-free zones to encourage people to walk and cycle.