Is private car ownership defunct? With road space limited and road usage growing, the debate on congestion and air quality in cities is heated. While opinions vary on what is to be done, people agree that a breakthrough is needed. Will it be a matter of P2P platforms, a technological overhaul of systems and modes of transport, policy reform - or a combination of the three? Journalist Matthew Gwyther talks to some of the leading thinkers and players in this space. Answering these and other transport and air-quality questions: Isabel Dedring, Global Transport Lead at ARUP; Nick Lester-Davis, Vice-Chair, European Road Transport Research Advisory; Jonathan Hampson, General Manager, Zipcar; Frank Kelly, Professor of Environmental Health, King's College London; and David Brown, CEO, Go-Ahead Group.