UF and NCSU Team up to Produce Tool to Estimate Vehicle Emissions using CORSIM Simulation Software

The USDOT has established strategic goals regarding livability and environmental sustainability in order to minimize the significant effect of transportation systems on the environment. These goals have motivated the need for accurate measurements or estimates of micro-scale (i.e., second or sub-second) vehicle Energy Use and Emissions (EU&E). The availability of such data is especially important considering the growing need to assess the environmental effectiveness of traffic and Intelligent Transportation System (ITS) management strategies such as ramp metering, managed lanes, traveler information systems, speed harmonization, and even connected vehicle systems. Since highway transportation accounts for large portions of the national annual emissions, transportation planners and engineers must pay special attention to these strategies to ensure that improvements in transportation operations also result in acceptable air quality conditions.

CORSIM is a microscopic traffic simulation software program used by many traffic analysts in the U.S. CORSIM models traffic at the individual vehicle level, and at a 1-second time resolution. The software is currently maintained by the McTrans Center at the University of Florida. While the traffic modeling aspects of the program have kept pace with the state-of-the-art, the emissions modeling aspect of the program has not been updated in over 20 years. In order to bring CORSIM into the 21st century, Scott Washburn, Ph.D., an associate professor at the University of Florida and Nagui Rouphail, Ph.D., a professor at North Carolina State University (NCSU), are working with emissions modeling expert Christopher Frey, Ph.D., an environmental engineering professor at NCSU on this STRIDE-funded project (see project description at /washburn-abstract-014s.)

Frey has long been concerned with the influence of traffic lights, road conditions, traffic congestion, and driving behavior on motor vehicle emissions in real-world situations. In an extensive 2003 study, Frey and his colleagues were able to analyze the emissions figures for various vehicle types in actual driving conditions by fitting vehicles with an onboard diagnostics system which records second-by-second engine and emissions data. Frey and his team then developed models for light-duty vehicles, transit buses, and heavy duty trucks based on specifics such as engine load, acceleration rates, and road grade. The data are analyzed using the EU&E estimation method founded on the concept of Vehicle Specific Power (VSP), which is a vehicle activity measure of engine load. In addition to the VSP model being sensitive to more roadway and vehicle factors than the current emissions modeling approach in CORSIM, it reflects current vehicle technologies and driving behavior. The incorporation of the VSP emissions estimation model into CORSIM will make it a valuable tool not only for evaluating traffic operations, but also one that can be used to assess the air quality impacts of various traffic management strategies. Furthermore, with such a tool, transportation planners and engineers can more reliably and accurately consider the potential tradeoffs in traffic performance and air quality.

In order to validate the VSP model once it is implemented in CORSIM, the researchers will compare CORSIM emissions estimates for an arterial roadway section in Gainesville and a freeway section in Orlando using the University of Florida Transportation Research Center vehicle that is equipped with a Portable Emissions Monitoring System (PEMS), which measures the emissions of CO2, CO, HC, and NOx as well as collecting GPS position data and vehicle engine state parameters.