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27 <br />process such that no trips can improve their travel times by using a different route. To better <br />capture the effects of congestion, the Triangle model was loaded sepazately for the a.m., p.m. and <br />off-peak time periods. Peak periods aze 4-hour periods. <br />3.11 Method of renortin~ VMT and speed <br />The Triangle regional model has the capability to provide output by peak period in addition to <br />daily output. Since the TRM can model peak period volumes and speeds, these must be used in <br />the air quality analysis. The vehicle kilometers of travel (VKT), is converted to vehicle miles of <br />travel (VMT). Vehicle miles traveled (VMT) used in the conformity determination aze from the <br />last iteration of the model. Each link in the roadway network carries a functional classification. <br />The VMT for each functional class is multiplied by an emissions factor. The North Carolina <br />Division of Air Quality (DAQ) provides the emissions factors based on MOBII.E6.2 output. <br />The MOBII.E6.2 model requires as an input the weighted speeds by functional classification. <br />This information can be derived directly from the model link data output. This first requires the <br />sepazation of the model link data into functional classification. The congested link speed in <br />mph can then be determined by converting the link distance to miles and dividing by travel time. <br />The congested speed is then weighted by the ratio of the link VMT to the system VMT for each <br />of the functional classifications. This input is then used for MOBII.E6.2. <br />Congested and uncongested speeds are calculated using the model output. The congested <br />speeds are sent to DAQ to determine actual emissions factors. <br />4. Regional Emission Analysis <br />In areas with an USEPA approved attainment demonstration or maintenance plan, an emissions <br />budget comparison satisfies the emissions test requirement of 40 CFR Part 93.118. For <br />pollutants for which an emissions budget has been submitted, the estimated emissions from the <br />transportation plan must be less than or equal to the emissions budget values. Emissions factors <br />were provided by DENR. <br />All parts of the Triangle Ozone Maintenance Area have emissions budgets, what parts are <br />covered by the Triangle Regional Model (TRM) and how each part was analyzed for each <br />pollutant in each comparison yeaz. <br />Four counties in the non-attainment azea are completely within the Triangle Regional travel <br />demand Model (TRM) boundary: Chatham (Baldwin, Center, New Hope and Williams Townships <br />which aze designated non-attainment), Durham, Orange and Wake. Person County is completely <br />outside of the TRM boundary. The other 3 counties, Granville, Franklin and Johnston, have parts <br />that are within the modeled area and parts that aze outside of the modeled area. <br />4.O.1. Sub-area emission budgets <br />Each county or, in the case of Chatham County, county portion, have NOz emission budgets. In <br />addition, Durham and Wake Counties have CO emission budgets. These Motor Vehicle <br />Emission Budgets were used in performing the emissions analysis. <br />19 <br />