APPENDIX E$_{ }$ E.2.6  Select Dispersion Models  CAL3QHC and CAL3QHCR are the two EPA-approved mobile source dispersion models used  to predict CO and PM (i.e., PM $_{10 }$and PM$_{2.5}$) concentrations, respectively, at sensitive receptor  locations adjacent to highway and roadway intersections 107 . Information on EPA’s recommended  models is detailed in EPA’s  Guideline on Air Quality Models  mentioned above.  The CAL3QHC model is an effective tool for predicting hourly CO emissions due to vehicles operating under free -flow conditions and from idling vehicles under stop- and-go  conditions (or queuing conditions)  near signalized intersection s. The model’s inputs include  roadway geometries, traffic data, receptor locations, meteorological conditions, and vehicular  emission rates (estimated using either EPA’s MOVES or California’s EMFAC). Additionally, it  incorporates intersection-specific parameters and detailed signal information (e.g., signal timing  and intersection lane as signments) to predict 1-hour and 8-hour CO concentrations at near-by  sensitive receptors.  The CAL3QHCR is the refined, yet independent version of CAL3QHC that has the capability to  predict 1-hour, 8-hour, 24-hour, and annual concentrations, with the use of a full year of hourly  meteorological and traffic data; thus CAL3QHCR is better suited for PM  hot-spot analyses.  Notably, when using the CAL3QHCR for PM hot -spot analysis highway and  roadway  intersection projects, its queuing algorithm should not be used. 108  CAL3QHCR should be used  for CO when a CAL3QHC analysis with conservative assumptions indicates a potential exceed the NAAQS.  The CAL3QHC and CAL3QHCR model inputs and their respective parameters are provided in  Table E-5  ( CAL3QHC and CAL3QHCR Model Input Data ) and further discussed in this section.  Additionally, EPA has also approved AER MOD as a recommended air quality model completing PM hot -spot analyses for different types of transportation projects  (e.g., parking  facilities). Refer to  EPA’s  Transportation Conformity Guidance for Quantitative Hot -Spot  Analyses in PM 2.5  and PM 10  Nonattainment and Maintenance Areas  mentioned above, for  complete information on selecting an appropriate air quality model.  107 EPA’s Technology Transfer Network (TTN) Support Center for Regulatory Atmospheric Modeling website at:  http://www.epa.gov/scram001/dispersion_prefrec.htm for latest model guidance, updates and revisions.  108 EPA,  Transportation Conformity Guidance for Quantitative Hot-spot Analyses in PM$_{2.5 }$and PM$_{10 }$Non- attainment and Maintenance Areas,  November 2013 [EPA-420-B-13-053],  http://www.epa.gov/otaq/stateresources/transconf/policy/420b13053-sec.pdf.  Model Inputs  Parameters  Units  Roadway Geometry  • Free flow link coordinates (x, y, z)  • Queue link coordinates (x, y, z)  • Mixing zone width  • Link Height  • Meters or feet  Traffic Data 1  • Traffic Volume  • Vehicle per hour  Table E-5. CAL3QHC and CAL3QHCR Model Input Data  98$_{ }$