High-Resolution Modelling of Carbon Dioxide Emissions Before and After the Implementation of a Designated Truck Lane

Abstract

This work seeks to assess the impact of adding a lane for slower trucks on a divided multilane highway on CO₂ emissions. A portion of the U.S. 101 highway in San Luis Obispo County in California consists of the Cuesta Grade which is a 2.75-mile segment with a 7% grade. A microsimulation software, VISSIM, was used in conjunction with the Environmental Protection Agency’s emissions model, MOVES, to estimate CO₂ emissions on the corridor before and after the construction of the third lane. It was found that CO₂ emissions <i>decreased</i> between 1998 (before) and 2012 (after the 2003 lane addition), but the effect of the truck lane was shown to be different for the northbound (uphill) and southbound (downhill) directions. The truck lane in the northbound direction exhibited a 9.5% decrease in volume with 10.7% decrease in emissions, and the southbound direction experienced a 20.3% increase in volume but 7.4% decrease in emissions. For the northbound (uphill) direction, emissions seemed to correlate more closely with traffic volumes while a sensitivity analysis revealed travel speeds had a more profound effect on southbound (downhill) emission rates. In the conclusion section, ideas to further validate the emissions estimate are discussed. Emissions seemed to correlate more closely with traffic volumes (uphill) while travel speeds had a more profound effect on southbound (downhill) emission rates. One factor to be accounted for is the change in volume which seems to play a much larger role in emissions than roadway features or topography.