Volume 2: Draft Gorst Planned Action Environmental Impact Statement

GORST PLANNED ACTION EIS | AFFECTED ENVIRONMENT, SIGNIFICANT IMPACTS, AND MITIGATION MEASURESThese zone systems provide the Kitsap model the geographic detail needed to better estimate and forecast localtraffic, while maintaining consistency with the PSRC model for data input, such as trip rates, population and landuse forecasts, etc.Within the Gorst UGA, the proposed land used assumptions for each model were broken down to each of the eightzones that make up the Gorst UGA. The trips that the model generated from these land use assumptions weredistributed to the roadway network via centroid connectors. Depending on the number of local roadways that passthrough the various zones, more than one centroid connector was included to provide a clear direction as tolocation of the origin and/or destination of the trips.Transportation NetworkThe roadway network is represented in the computer as a series of links (roadway segments) and nodes(intersections). Characteristics such as capacity, length, speed, and turning restrictions at intersections are codedinto the network. The approach taken in developing the transportation network was similar to that employed inTAZ development. It started with the PSRC network as the base, but a more detailed network was developed insideKitsap County. Within the Gorst UGA each of the existing roadways that provided a connection to either arterialroadways and/or state highways was included. Roadway that serviced a small residential community without adirect connection to larger roadways was not included in the network. It is assumed that these types of roadwaysare best replicated in a group and reflected as centroid connectors.Trip GenerationThe trip generation step estimates the total number of trips produced by and attracted to each TAZ in the studyarea. The trips are estimated using statistical data that take into account population and household characteristics,employment information, economic model output, and land use information. Trip generation in the Kitsap modelis based on the procedures developed by PSRC. The PSRC model is a cross-classification model, which requires landuses to be cross-classified by income groups, number of workers, number of college-aged persons, and number ofschool-aged persons. For non-residential land uses, it uses a linear regression procedure. The PSRC procedureapplied only to the Kitsap internal zones (1 through 411). For other zones outside the county border, trip data fromthe PSRC model were directly imported.Trips generated are categorized by their general purpose; these are listed below.• Home based work trips—any trip with home as one end and work as the other end• Home based college trips—any trip with home as one end and college as the other end• Home based other trips—any non-work trip with home as one end• Non-home-based trips—any trip that does not have home as either endThe trip generation model generally estimates the number of trips that are generated per household during theanalysis period for each of the purposes under consideration. For its output, the trip generation model estimatesthe total number of trips produced in each TAZ and the total number of trips attracted to each TAZ, categorized bytrip purpose.Trip DistributionThe trip distribution step allocates the trips estimated by the trip generation model to create a specific zonal originand destination for each trip. This is accomplished through use of the gravity model, which distributes tripsaccording to two basic assumptions:1. More trips will be attracted to larger zones (the size of a zone is defined by the number of attractionsestimated in the trip generation phase, not the geographical size).Draft | June 2013 3-166