Anti-pollution activists blocked a busy central London road on Tuesday evening, causing long delays.
Campaigners staged a protest against air pollution for the second time in two days as they sat across Marylebone Road, near Baker Street station, during rush hour.
Images from traffic cameras show a group of activists sat in the middle of the road with a large banner preventing motorists from passing.
Transport for London (TfL) warned commuters at about 7pm to expect “long delays” in the area.
Photos were shared on social media by campaign group Stop Killing Londoners, who held up a large red banner reading: “Cut air pollution.”
The Metropolitan Police Service is yet to respond to a request for comment. It is not known if any arrests were made.
It is the second protest in the same number of days by anti-pollution protestors.
Demonstrators shut down Tower Bridge on Monday after they staged a protest against air pollution where reportedly resulted in seven arrests.
A report published on Tuesday revealed that millions of people living in dozens of UK cities are inhaling air the World Health Organisation (WHO) considers too dangerous to breathe.
The report found that 802 London schools and a high proportion of the capital’s hospitals and clinics were located in highly polluted areas “potentially putting some of society’s most vulnerable at risk”.