Study of Emissions Benefits of Commercial Vehicle Lane Management Strategies

Abstract

Traffic congestion mitigation has been proposed as a strategy to help attain air quality goals. A better understanding of the full effects of congestion on heavy-duty (HD) vehicles is needed because HD vehicles contribute a large share of on-road emissions and are more sensitive to speed than light-duty vehicles. This research shows that the estimated emissions effects of congestion mitigation vary greatly by pollutant and are sensitive to the assumed travel demand elasticity, initial congestion level, and lane management strategy. Analysis of four managed lane scenarios shows that vehicle class–segregated facilities tend to outperform general purpose lane strategies in emissions reductions. Although potentially controversial, from an emissions perspective, conversion of a general purpose lane to a truck-only lane may produce more emissions benefits than adding either a truck-only lane or a general purpose lane. Furthermore, the expected emissions benefits from truck-only lane conversion are robust to uncertainty in travel demand elasticity. This research demonstrates the emissions trade-offs inherent in congestion management between emissions rates and travel volumes by vehicle class and presents a concise methodological framework that can be readily applied in other contexts for sketch-level analysis of emissions effects from vehicle class–targeted congestion management.