Hong Kong is a city of extremes. It is one of the most densely populated places on the planet, with more than 7 million people living on just 15% of the land area.
This presents an enormous challenge for its transport system and its residents. It also creates a huge amount of pollution.
Now, the Hong Kong hopes to tackle this by overhauling its entire transport system; something it hopes will also cut carbon emissions in half by 2020.
Adam Shaw meets Professor Anthony Hedley – a scientist who monitors the cost of roadside pollution. He describes the levels in the city as “astronomical”.