Town of Summerville Planning Area - BCD Council of Governments

Transportation Model AnalysisThe BCDCOG employs a traditional 4‐step Travel Demand Model (TDM): 1) Trip Generation 2) TripDistribution 3) Mode Split and 4) Network Assignment ‐ to forecast future year traffic volumes on theregion’s roadways. There are two major inputs to this model – socio‐economic data (SE Data), todetermine the trip‐making characteristics; and road networks, to assign these trips. SE data is reported byTraffic Analysis Zones (TAZ). TAZ are based on census geographies. All major roads (almost anything aboveneighborhood street level) are modeled in the road network. As a part of the Town’s Traffic Plan, Carter &Burgess modified these inputs to better reflect the Town’s land use activities and transportation needs.Changes were made to the road network and the SE data by augmenting the TAZ data. These changes aredescribed below.Socio‐economic Data (SE Data):As mentioned above, trip‐making characteristics of the study area are determined by demographiccomposition. In the current model set up, these variables are analyzed in a series of algorithms to rendertrip generations and distribution steps of the process for each TAZ: total number and average size ofhouseholds, total number of students, number of households by household characteristics,presence/number of vehicles and workers, total number of jobs, and number of jobs in differentcategories. .As a part of Town’s Transporation Plan, Carter & Burgess updated data for the following TAZs: 801‐802,804‐806, 816‐818, 820‐828, 830‐837, 839‐846, 854; the control total for population and jobs for theSummerville area remain the same. (Figures 2.4 & 2.5)Figure 2.4 - TAZ Map: Populationforecast re-allocation in SummervilleFigure 2.5 - TAZ Map - EmploymentforecastData: C & B Traffic PlanData: C & B Traffic PlanAppendix 1: BCDCOG Travel Demand Modeling Scenarios Page 3