Increasing population and employment density in metropolitan areas could reduce vehicle travel, energy use, and CO2 emissions from less than 1 percent up to 11 percent by 2050, a new report has said.
The report is a new congressionally mandated report from the National Research Council in the US.
Assuming compact development is focused on new and replacement housing, as converting existing housing to higher densities could be prohibitively difficult, significant increases in density would result in modest short-term reductions in personal travel, energy use, and CO2 emissions.
However, these reductions will grow over time.
According to the committee that wrote the report, the most reliable research studies estimate that doubling residential density in a metropolitan area might lower household driving between 5 percent and 12 percent.
If higher density were paired with more concentrated employment and commercial locations, and combined with improvements to public transit and other strategies to reduce automobile travel, household driving could be lowered by as much as 25 percent.
By reducing vehicle use, petroleum use and CO2 emissions would also be lessened.
In order to quantify the potential effects of compact development, the committee developed illustrative scenarios, looking forward to 2030 and 2050.
If 75 percent of new and replacement housing units in the US were developed at twice the density of current new development, and individuals drove 25 percent less - the committee's upper-bound scenario - personal travel, fuel use, and CO2 emissions would be reduced by 7 percent to 8 percent, relative to a base case, by 2030, and by 8 percent to 11 percent by 2050.
If only 25 percent of housing units were developed more compactly, and residents drove 12 percent less, then personal travel, fuel use, and CO2 emissions would be reduced by approximately 1 percent by 2030, and by 1.3 percent to 1.7 percent by 2050.
If in this lower-bound scenario, residents drove only 5 percent less, then personal travel, fuel use, and CO2 emissions would be reduced by less than 1 percent by 2050.