Where’s my bus?
Even in cities with good public transportation, some areas can be 'transit deserts,' where demand exceeds supply. Living in these zones makes it hard to access good jobs, health care and other services.
Sao Paulo, Brazil, 2013. Subways abound in fine particles often carried by brakes or trains.
Diego Torres Silvestre/Flickr
Subways seem like the perfect solution to improve air quality in cities. But what about air quality underground?
The St Petersburg attack shows how engineering and psychology can help optimise how people are evacuated in a disaster.
Maintenance has been pushed off so much that the D.C. Metro needs to shut lines down for months for repairs.
How did urban public transport in America, like much of our infrastructure, get to be in such bad shape? Will millennials help turn it around?