In December of 1952, a cold weather system descended on London and caused a buildup of factory smog so severe that visibility was reduced to just a few feet.

Now known as the Great Smog of 1952, the event forced London officials to finally take steps to alleviate the city’s ongoing air-pollution problems.

Since then, London has made sweeping reforms that have significantly improved the city’s air quality.

London’s air quality might be a whole lot better than it was in the 1950’s, but there’s still room for improvement.

City officials estimate that roughly 9,400 premature deaths happen every year as a result of illnesses caused by long-term exposure to air pollution.

That’s why mayor Sadiq Khan is planning to phase out diesel buses and replace them with hybrid-engine and zero-emission models over the next four years.

  • Starting in 2018 the city will stop adding diesel models to its iconic fleet of red double-decker buses.
  • Furthermore, all new single-deck buses in the city will be zero-emission models.

“I want London to become a world leader in hydrogen and electric bus technology,” said Khan in his announcement speech. “Transforming London’s bus fleet by accelerating the introduction of zero-emission buses is important and I plan to work with bus manufacturers, other cities, the European Commission and the C40 Climate Change Leadership Group of Cities to move this agenda forward.”

Khan made the announcement in conjunction with the unveiling of a new hydrogen-powered bus that will begin trials on London roads next year.

Currently, London has a total of 79 zero-emission buses in service, 51 of which are battery powered. The city also maintains three fully-electric bus routes.

After earning a reputation for being one of the most polluted cities in the world during the 20th century, London has found itself at the forefront of the movement to improve urban air quality worldwide.