Cities, traffic, and CO2: A multidecadal assessment of trends, drivers, and scaling relationships (6 page pdf, Conor K. Gately, Lucy R. Hutyra, and Ian Sue Wing, Proceedings of the National Academy of Sciences of the USA (PNAS), Apr. 9, 2015)
Also discussed here: Maps pinpoint where cars pollute the most (Barbara Moran-Boston University, Futurity, Apr. 15, 2015)
Today we review research into the contributions that vehicles make to greenhouse gas emissions over the last 33 years on urban roads in the USA where 87% of the counties have low population densities (or are sprawled towns and cities). Results indicate that top-down estimates of national or regional GHG emissions may be as much as 50% in error unless these emissions are estimated at the scale of roads and streets (approx 1 km resolution) as opposed to estimating them from population only. The authors suggest that the contributions from on-road emissions will likely increase as population and road densities increase in the future, suggesting that carbon policy makers focus on per capita emissions (which in turn would be linked to low or high driving rates) to capture the greater emissions from urban hotspots.
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