A dormant 'cash mountain' marks a nadir for London's contactless travel card, but trouble has been brewing for some time.
Cities are expanding upwards and downwards, as well as outwards. With urban density also increasing, moving people efficiently around the city, often using ageing infrastructure, is quite a challenge.
Millions of Americans rely on public transit to get to school, work or stores, but many can't get the service they need. 'Uberizing' transit by offering more options on demand could fill the gaps.
Many Americans live in transit deserts – areas where demand for transit exceeds the supply. To fix these gaps, we need to find and map them so agencies can add transit options in the right places.
More than 200 mayors have committed their cities to stick with the Paris climate deal no matter what the US does. Electric vehicles offer a promising route to making good on that pledge.
A combination of transit-oriented centres, inclusionary zoning and a special rate on land instead of stamp duty could make housing more affordable by cutting congestion, development and travel costs.
To maximize the benefits while minimizing the risks, we need to know how ride-share companies will affect public transportation.
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?