Framework and Demonstration of Simulations of Environmental Impacts from Traffic on Highway Construction Work Zones

The objective of this study was to develop a framework for determining the fuel use and environmental impacts caused by construction work zones (CWZs) on a range of vehicles and to produce initial calculations of these impacts by modeling traffic closure conditions for highway maintenance and rehabilitation (M&R) activities. The framework was developed and demonstrated in several scenarios. The study included three common highway categories—freeways, multi-lane highways, and two-lane highways—and common California vehicle types. The framework uses realistic drive cycle values and CWZ operation scenarios as inputs to the simulation software MOtor Vehicle Emission Simulator (MOVES) to estimate total fuel consumption and air pollutant emissions. In this study, the framework was demonstrated using three CWZ operations under different traffic congestion levels: light, medium, and heavy. Fuel consumption and pollutant emissions results obtained for the CWZ operation scenario with and without congestion were compared with those for a no-CWZ, no-congestion scenario. In the simulation results for a freeway with a CWZ and heavy congestion, fuel consumption increased by 85% and the CO2 equivalent (CO2-e) emissions increased by 86%, NOx by 62%, SOx by 85%, and PM2.5 by 128%. In the multi-lane highway scenarios, fuel consumption increased by 85%, and CO2-e emissions increased by 88%, NOx by 75%, SOx by 87%, and PM2.5 emissions by 129% for a CWZ with heavy congestion. Lessening traffic congestion in a CWZ from heavy (average speed 5 mph) to medium (average speed 25 mph for a freeway section and 15 mph for a multi-lane road section) reduced fuel consumption by 40% on a freeway and 33% on multi-lane highway. This study also included use of a pilot car in a CWZ on a two-lane road. This approach was undertaken to estimate the possible benefits of different CWZ lane closure strategies and traffic management plans. The pilot-car operation scenario results indicate that a one-lane closure with pilot-car operation on a two-lane road might consume 13% more fuel because of idling time and the slow movement of vehicles following the pilot car. This scenario generated emissions increases of 10% for CO2-e, 14% for NOx, 13% for SOx, and 65% for PM2.5. The results of these scenarios indicate that the impacts from heavy vehicles far exceed those from smaller vehicles in CWZs. Phase 2 of the study will develop methods for pavement management, conceptual evaluation, and project design that consider construction closures by implementing this life cycle assessment framework. These methods will also be used in studies to evaluate pavement design lives (20 years versus 40 years) and pavement selection for truck lanes and in-place recycling and to evaluate lane closure schedules and tactics to minimize CWZ impacts on highways by using project-specific traffic congestion levels.