By: Alexander Skabardonis
This white paper summarizes the findings from a critical review of literature supplemented by interviews with subject experts and public agency staff on environmental impacts of congestion management strategies. Emphasis is placed on the quantitative impacts of operational strategies on vehicle miles traveled (VMT), and greenhouse gas (GHG) pollutant emissions. Examples ofstrategies include traffic signal timing, ramp metering, transit signal priority, variable speed limits, temporal shoulder use, dynamic lane utilization, integrated corridor management, incident management and traveler information and guidance. The review also addresses the environmental impacts of emerging transportation technologies such as connected andautomated vehicles (CAVs) and the challenges to accurately assess their impacts, given the limitations of existing modeling tools to accurately model driver-vehicle characteristics and interactions, much less predict their broader impacts. Also, the impacts of CAVs are difficult to estimate because theydepend on the penetration rate in various operating environments, which will be a function of vehicle ownership and operation costs, consumer preferences, intended vehicle uses, operating environment, and public policy.Recommendations are provided for developing analysis procedures to predict the interactions of congestion measures that reduce GHG and the VMT changes in the short and long term.