Expanding carpool lanes

Transport. Res. D 56, 155–174 (2017)

Credit: GREEN STOCK MEDIA/ALAMY STOCK PHOTO

In the United States, the transportation industry accounts for a large proportion of total greenhouse-gas emissions. Road-based emissions — those associated with passenger and other vehicles — have grown rapidly in recent decades, necessitating the implementation of policy measures to help combat anthropogenic climate change, but also reduce air pollution. High-occupancy-vehicle (HOV) lanes are one such strategy, and aim to reduce the number of vehicles on the road by encouraging carpooling. Roxana Javid from Savannah State University, USA, and colleagues develop a multiple regression model to quantify the environmental benefits of a modest expansion in HOV lanes across the United States.

In response to increased HOV lanes, many densely-populated states are found to have considerable potential to reduce CO₂ emissions; for example, in the District of Columbia, New York, New Jersey, Maryland, California, Massachusetts and Hawaii, reductions could reach 1–4.5%. The smallest reductions are projected for the sparsely populated northern Great Plains. In total, up to 1.83 million tons CO₂ could be saved annually, representing 0.23% of US passenger car-related CO₂ emissions. Thus, increased HOV lane infrastructure offers a means to mitigate, at least partially, vehicle emissions.