Proc. Natl Acad. Sci. USA 108, 16554–16558 (2011)

Credit: © MACMILLAN NEW ZEALAND

What type of vehicles most benefit society over their lifetime per dollar spent on building, maintaining and fuelling them? Perhaps surprisingly, it turns out to be hybrid and plug-in hybrid electric vehicles, according to group of researchers led by Jeremy Michalek of Carnegie Mellon University in Pittsburgh, Pennsylvania, USA.

These vehicle classes outdid conventional cars and battery-powered electric vehicles in their analysis. The work takes into account, for example, the power plant emissions associated with charging a plug-in car, the direct costs of oil as well as the military expense associated with defending against disruption in its supply, the impact of greenhouse-gas emissions from exhaust pipes, and vehicle recycling and land filling. The results are subject to certain variables, such as oil price and battery life.

The authors argue that some of the US subsidies for encouraging emission reductions in transportation should be targeted at potential buyers of hybrids, which offer the most social benefit per dollar despite their small battery packs.