Fresh off the USA’s public research pipeline is this fascinating study (HT: TC) of compact urban forms and their impact on vehicle movements and emissions. Auckland councils have been compacting urban forms for a while now, but the arguments have always been qualitative. Transport efficiencies are invariably cited, but this research suggests they’re pretty modest.
The punchline seems to be this.
the committee believes that reductions in VMT, energy use and CO2 emissions resulting from compact, mixed-use development would be in the range of less than 1 percent to 11 percent by 2050, although the committee disagreed about whether the changes in development patterns and public policies necessary to achive the high end of these findings are plausible.
Set alongside similarly small agglomeration benefits, these low transport efficiency estimates do not help the case for a compact Auckland. The USA authors do endorse compact urban form policies, but as an article of faith rather than a deduction from their analysis.