When Ebenezor Howard was writing Garden Cities of Tommorrow he thought about their ideal size. He took as a model a reasonably well functioning small English Town, with its own school, hospital etc, and decided on Hitchin. Which had a population of around 20,000 in 1900, and around 35,000 now (declining then like most market towns, till commuter growth to London took off in the 1930s). Howard assumed a maximum population of around 32,000 for a Garden City so may have assumed continued growth at Htchin.
One thing I discovered was that Howard’s assumptions were based on the high household size of the time, and even at the relatively high densities he assumed in his book (as opposed to the lower ones designed by Unwin) it was not possible to fit five walkable schools into the catchment of a single secondary school or station, with modern family sizes) unless you increased the density to over 100 DPH, or had a polycentric form.
The Abercrombie Plan had a number of quite small new towns. For example Beconsfield only had a population today of 12,000. Some of the new Towns such as Stevenage were enlarged several times from their original design size.
By the mid 1960s lessons were being learned from the first generation of New Towns. The most successful were the lragest ones with the best transport connections. The Treasury pressed for the third generation of new towns – Milton Keynes and Telford – to be much larger, new cities of around 1/4 million design size, not just new towns.
I think the Treasury at the time were influenced by the first modern thinking in regional science emanating out of France. Growth pole theory suggested you would get higher economic growth from urban economies of scale from larger settlements. This has been borne out by history as for many years MK has been Britain’s fastest growing town.
Apparently Homes England have signaled they wish to see larger Garden Communities – of around 10,000. For the Arc they have said at conferences they are looking at 50,000 minimum. 10,000 is an arbitrary number. You need to think in terms of units a settlement around multiples of a primary school then secondary school. For a typical five feeder school secondary and typical pupil yields that equates to around units of 12,800 population.
Then you have the problem that Oxford and Cambridge are structurally very difficult cities to expand, with many benefits from quality of life, access to open space, walkability and cyclability owing to their compact nature. Once the current local plan round of growth is over there will be only limited opportunities to grow on either cities edge. There certainly is not a case to grow from there currently populations (around 150,000) to MK size (250,000), on the other hand you could grow MK to 1/2 a million (if you include adjoining areas in Bucks and Beds) and that is the ambition. Though not necessarily with the support of Central Beds or Bucks.
So even this crude calculation suggests a crude broad ‘landing zone’ for new settlement design size in the Arc. Grow MK by an MK, and to protect the compact form of Cambridge and Oxford, grow another Oxford and another Cambridge nearby – within short transit distance. That makes up around half of the 1.5million needed. The rest going on growth in Northamptonshire and the rest of Bedfordshire, as well as growth around smaller settlements across ll four counties.
This is managable and avoids the much worse alternative of scattered shotgun like pot shots at every village you see in call for sites.
This is not ‘concreting over the countryside’ it is its very opposite as a conventional local plan driven approach would produce. If you argue against that you are arguing Oxford or Cambridge should never have been built. Each takes up only a tiny front print of the huge arc area and the alternative would be massive sprawl. The new towns like old Oxford and Cambridge would demand their own Green Belts to ensure they dont sprawl beyond their optimum design size. Nor would they be huge estates of car orientated development, as we see for example in Northampton. International nest practice suggests a string of pearls approach based around transit orientated development (15 minute neighbourhoods) feeding into a dense urban core – much like Fred Pooleys original – but never built, plan for MK.