Skip to main content
Loading…
This section is included in your selections.

Transportation forecasting is an art and not an exact science. The method described will not accurately predict the future 20-year traffic counts, as it will attempt to discover a relationship between current traffic patterns and the new traffic generated from land use alterations. The purpose of linking land use and transportation in the Comprehensive Plan is that they are each predisposed to the occurrence of the other. All land use decisions should be based on traffic impacts and the ability of the jurisdiction to maintain the existing transportation facility to standard. An underutilized or overbuilt transportation facility has the tendency to guide growth into the area, whereas, overcapacity deters growth when expensive road improvements must accompany the development. This reasoning is why a lower level of service standard is acceptable in an urban growth area – it guides growth into an area where infrastructure can best support growth.

County road deficiencies will be analyzed and reported in subregional plans. Transit deficiencies are listed in CCC 31.02.430 and nonmotorized deficiencies are analyzed in the bicycle plan, CCC 31.02.440. All marine and air transportation deficiencies are deferred to the Port of Port Angeles Comprehensive Scheme of Harbor Improvements, December, 1986. All State highway deficiencies will be deferred to the Peninsula Regional Transportation Planning Organization Regional Transportation Plan.

The Highway Capacity Manual (1985) software is the methodology to determine highway level of service as revised by the Florida Department of Transportation to accept rural, transitioning, and urban land uses. This software was selected for two reasons: (1) the reference to land use and (2) to achieve consistency with State highways and regionally significant roads. The Peninsula Regional Transportation Planning Organization (PRTPO) is using the same software to determine level of service on regionally significant highways and roads. The County Comprehensive Plan endorses the regional transportation planning of the PRTPO and assumes the level of service standards, deficiencies and system needs of the State highways. A sophisticated traffic computer modeling package, Tmodel II, will be used by the County in cooperation with local jurisdictions. The model will contain the federal classified roads that qualify for ISTEA Surface Transportation Program funds which are rural major collectors, urban collectors, minor and principal arterials. The model will forecast the allocation of traffic to the network of collectors and arterials. Case by case, the new traffic generated from a development can be loaded onto the network to see if the level of service remains adequate. The traffic model will be the best tool available to monitor concurrency.

For comprehensive planning purposes, the County Road Information System (CRIS) was linked to a geographic data layer in the PC ARC/INFO Geographic Information System (GIS). The CRIS contains annually updated road design and road conditions information. GIS analysis and mapping provided a vehicle for deficiency inventory and interactive public involvement. It also performed the trend analysis for forecasting traffic. Traffic Analysis Zones (TAZs) were delineated from census block numbering areas with some census block modification. The TAZs were analyzed by the GIS for zoning and land use characteristics for the “do nothing” case. The assumption is that as current land use conditions remain and the influx of population rises, growth will occur in the undeveloped regions with development potential. The 1990 Census was used in a linear projection forecast model to determine the amount of growth to be received by the subcensus area. The growth is distributed into the TAZs by proportion of undeveloped parcels. Regional land use alternatives are analyzed for modifying growth patterns of residential and commercial/industrial development. As densities increase or decrease, average daily traffic (ADT) per household is calculated as 10 trips per day, according to the Institute of Transportation Engineers Trip Generation (ITE) Manual, 5th Edition.

The PRTPO has selected a menu of transportation growth rates based on the wide range of census data from the four-county region: Mason, Kitsap, Jefferson and Clallam. The regional road system is analyzed with 1.5 percent, three percent and 4.5 percent transportation growth rates. Clallam County should plan for future regional transportation needs (County arterials) using the lowest transportation growth rate of 1.5 percent, realizing that east and west County will not experience the same growth. For major collectors and streets, the County should plan for future transportation needs using 50 percent of potential build-out as indicated on the County comprehensive land use plan.