Characterizing the Impact of Nighttime Construction on Traffic-Related Emissions

Nighttime road maintenance and construction work is most commonly initiated where it is impractical or highly undesired to close traffic lanes on certain high-volume roadways during normal daylight hours. There is a lack of knowledge of the expected changes in emissions associated with moving construction activities to the nighttime. It is commonly expected that when construction activities are shifted to the nighttime, reduced traffic congestion could result in lower traffic-related emissions. The study presented in this paper investigated the air quality impacts of nighttime construction through three case studies and a modeling framework combining well-calibrated traffic microsimulation and the Environmental Protection Agency’s (EPA) MOtor Vehicle Emission Simulator (MOVES) emissions model. Simulation test beds were developed in VISSIM for each case study. The test beds replicated roadway and work zone characteristics including geometry, posted speed, and other relevant traffic control (e.g., signal timing on the arterial) at each study site. The case study sites were selected to encompass different traffic volumes, vehicle compositions, lane configurations, posted speeds, and traffic control. The results from the case studies illustrated that nighttime construction has a significant impact on traffic activities and emissions when directly compared to a daytime work zone scenario. Most of these impacts are directly attributable to the considerably lower traffic volumes during nighttime compared to daytime. However, important effects also occur because of the average behavior of vehicles through a work zone under different lane closure scenarios.