In his review of Ed Glaeser's book (Triumph of the City), my colleague Olmo Silva draws attention to one of the key policy proposals - build up, not out.
UK policy in this area is mixed. Home ownership favours non-urban living (because private renting of flats eases multi-occupancy problems). Relative to the US, we have abolished mortgage interest deductions for owner occupiers (a plus) but we have many policies that push for greater home ownership (a minus). Congestion charging in London plus high fuel prices tend to push people away from suburbs built around the car towards urban friendly public transport. Public transport spending is higher in the UK than the US, although we are just about to see large falls in expenditure (and a lot of money likely wasted on high speed 2).
Planning policy in emphasising brownfield over greenfield development makes the development that occurs in cities denser, but at the risk of some development occurring away from cities that would otherwise have occurred there. The greenbelt constrains development at the edges of the cities but at the danger of "leapfrogging" resulting in long commutes by rail or car. In terms of building up, London's mayor has just reinforced restrictions on historic sight lines, while London's tallest building (the Shard) took many years to get approval.
Although more pronounced in the US, UK cities still educate a disproportionate number of our poor children. Housing policy (including supply restrictions and the emphasis on mixed use) mean that middle income families increasingly opt for non-urban homes as the only way of avoiding schools that they feel will not adequately provide for their children.
Improving urban policy in the UK will require us to grapple with these difficult issues. Unfortunately, this is likely to prove difficult for all our political parties.