Carbon Monoxide Screen for Signalized Intersections COSIM, Version 3.0: Technical Documentation

The Illinois Department of Transportation (IDOT) currently uses the computer screening model Illinois CO Screen for Intersection Modeling (COSIM) to estimate worst-case CO concentrations for proposed roadway projects affecting signalized intersections. The original model was developed as part of the Illinois Transportation Research Center (ITRC) research project IIIA-H1, FY 97, completed in October 1999. Modeled results from Version 1.0 and 1.1 of COSIM are based on the U.S. Environmental Protection Agency???s (USEPA) mobile source emission model, MOBILE5b, and roadway dispersion model, CAL3QHC v 2.0 (Larson, 1999). The second version of COSIM was released in 2003. Version 2.0 incorporated new emission factor (EF) tables developed using USEPA???s updated version of the MOBILE model called MOBILE6. In addition to updating the emission factors used in COSIM, pre-screen criteria for determining when COSIM needs to be used for a roadway project were developed and incorporated into COSIM as a Pre-Screen feature (Larson, 2003). In 2007, regulatory changes in the Illinois vehicle Inspection and Maintenance (I&M) program prompted the Illinois Environmental Protection Agency (IEPA) to recommend that IDOT update COSIM with new EF tables using the MOBILE6.2 model. Based on this recommendation, IDOT and the Illinois Center for Transportation (ICT) provided funding to update the COSIM model. As part of the update, IDOT also requested that the methodology used in creating the original Pre-Screen criteria be reevaluated and possibly revised based on the findings of the evaluation. This report provides technical documentation on the updates and revisions made to Version 3.0 of COSIM finalized in June 2008.ICT R27-7published or submitted for publicationis peer reviewe