Carbon monoxide screen for signalized intersections COSIM, version 3.0 : technical documentation.
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Carbon monoxide screen for signalized intersections COSIM, version 3.0 : technical documentation.

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    • Abstract:
      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.

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