We're building about a quarter of the new homes we'd need to be building in order to fix housing, and we're already running out of sites. We need a new plan. We should make full use of our rail network. With a few investments, one rail line could be moving as many people as a forty lane motorway. We should start with the transport system and work backwards, because it's much harder to build a high-performing transport system in an existing city than it is to build a new neighbourhood around an existing transport system.