Chapter 18.180


18.180.010    Transportation impact analysis.

18.180.010 Transportation impact analysis.

(1) Purpose. The purpose of this section is to coordinate the review of land use applications with roadway authorities and to implement Section 660-012-0045(2)(e) of the state Transportation Planning Rule, which requires the county to adopt a process to apply conditions to development proposals in order to minimize impacts and protect transportation facilities. The following provisions also establish when a proposal must be reviewed for potential traffic impacts, when a transportation impact analysis or transportation assessment letter must be submitted with a development application in order to determine whether conditions are needed to minimize impacts to and protect transportation facilities, the required contents of a transportation impact analysis and transportation assessment letter, and who is qualified to prepare the analysis.

(2) When a Transportation Impact Analysis Is Required. The county or other road authority with jurisdiction may require a transportation impact analysis (TIA) as part of an application for development, a change in use, or a change in access. A TIA shall be required where a change of use or a development would involve one or more of the following:

(a) The development generates 25 or more peak-hour trips or 250 or more daily trips.

(b) An access spacing exception is required for the site access driveway(s) and the development generates 10 or more peak-hour trips or 100 or more daily trips.

(c) The development is expected to impact intersections that are currently operating at the upper limits of the acceptable range of level of service during the peak operating hour.

(d) The development is expected to significantly impact adjacent roadways and intersections that have previously been identified as high crash locations or areas that contain a high concentration of pedestrians or bicyclists such as school zones.

(e) A change in zoning or a plan amendment designation.

(f) A TIA is required by ODOT.

(3) When a Transportation Assessment Letter (TAL) Is Required. If the provisions of subsections (2)(a) through (f) of this section do not apply, the applicant’s traffic engineer shall submit a transportation assessment letter to Crook County planning department demonstrating that the proposed land use action is exempt from TIA requirements. This letter shall outline the trip-generating characteristics of the proposed land use and verify that the site-access driveways or roadways meet Crook County’s sight-distance requirements and roadway design standards.

(4) Preparation of a TIA or TAL. A professional engineer registered by the state of Oregon, in accordance with the requirements of the road authority, shall prepare the TIA or TAL. If preparing a TIA, the content and methodologies of the analysis shall conform to the requirements of subsections (5) to (13) of this section.

(5) Contents of a Transportation Impact Analysis. As a guide in the preparation of a transportation impact analysis, Crook County recommends the following format be used to document the analysis:

(a) Table of Contents. Listing of all sections, figures, and tables included in the report.

(b) Executive Summary. Summary of the findings and recommendations contained within the report.

(c) Introduction. Proposed land use action, including site location, building square footage, and project scope. Map showing the proposed site, building footprint, access driveways, and parking facilities. Map of the study area, which shows site location and surrounding roadway facilities.

(d) Existing Conditions. Existing site conditions and adjacent land uses. Roadway characteristics (all transportation facilities and modal opportunities located within the study area, including roadway functional classifications, street cross section descriptions, posted speeds, bicycle and pedestrian facilities, on-street parking, and transit facilities). Existing lane configurations and traffic control devices at the study area intersections. Existing traffic volumes and operational analysis of the study area roadways and intersections. Roadway and intersection crash history analysis.

(e) Background Conditions (without the proposed land use action). Approved developments and funded transportation improvements in the study area. Traffic growth assumptions. Addition of traffic from other planned developments. Background traffic volumes and operational analysis.

(f) Full Build-Out Traffic Conditions (with the proposed land use action). Description of the proposed development plans. Trip-generation characteristics of the proposed development (including trip reduction documentation). Trip distribution assumptions. Full build-out traffic volumes and intersection operational analysis. Intersection and site-access driveway queuing analysis. Expected safety impacts. Recommended roadway and intersection mitigations (if necessary).

(g) Site Circulation Review. Evaluate internal site access and circulation. Review pedestrian paths between parking lots and buildings. Ensure adequate throat depth is available at the driveways and that vehicles entering the site do not block the public facilities. Review truck paths for the design vehicle.

(h) Turn Lane Warrant Evaluation. Evaluate the need to provide turn lanes at the site driveways.

(i) Conclusions and Recommendations. Bullet summary of key conclusions and recommendations from the transportation impact analysis.

(j) Appendix. Traffic counts summary sheets, crash analysis summary sheets, and existing/background/full build-out traffic operational analysis worksheets. Other analysis summary sheets such as queuing and signal warrant analyses.

(k) Figures. The following list of figures should be included in the transportation impact analysis: site vicinity map; existing lane configurations and traffic control devices; existing traffic volumes and levels of service (all peak hours evaluated); future year background traffic volumes and levels of service (all peak hours evaluated); proposed site plan; future year assumed lane configurations and traffic control devices; estimated trip distribution pattern; site-generated traffic volumes (all peak hours evaluated); full build-out traffic volumes and levels of service (all peak hours evaluated).

(6) Study Area. The study area shall include, at a minimum, all site-access points and intersections (signalized and unsignalized) adjacent to the proposed site. If the proposed site fronts an arterial or collector street, the study shall include all intersections along the site frontage and within the access spacing distances extending out from the boundary of the site frontage. Beyond the minimum study area, the transportation impact analysis shall evaluate all intersections that receive site-generated trips that comprise at least 10 percent or more of the total intersection volume. In addition to these requirements, the county roadmaster (or designee) shall determine any additional intersections or roadway links that might be adversely affected as a result of the proposed development. The applicant and the county roadmaster (or designee) will agree on these intersections prior to the start of the transportation impact analysis.

(7) Study Years to Be Analyzed in the Transportation Impact Analysis. A level-of-service analysis shall be performed for all study roadways and intersections for the following horizon years:

(a) Existing Year. Evaluate all existing study roadways and intersections under existing conditions.

(b) Background Year. Evaluate the study roadways and intersections in the year the proposed land use is expected to be fully built out, without traffic from the proposed land use. This analysis should include traffic from all approved developments that impact the study intersections, or planned developments that are expected to be fully built out in the horizon year.

(c) Full Build-Out Year. Evaluate the expected roadway, intersection, and land use conditions resulting from the background growth and the proposed land use action assuming full build-out and occupancy. For phased developments, an analysis shall be performed during each year a phase is expected to be completed.

(d) Twenty-Year Analysis. For all land use actions requesting a comprehensive plan amendment and/or a zone change, a long-term level-of-service analysis shall be performed for all study intersections assuming build-out of the proposed site with and without the comprehensive plan designation and/or zoning designation in place. The analysis should be performed using the future year traffic volumes identified in the transportation system plan (TSP). If the applicant’s traffic engineer proposes to use different future year traffic volumes, justification for not using the TSP volumes must be provided along with documentation of the forecasting methodology.

(8) Study Time Periods to Be Analyzed in the Transportation Impact Analysis. Within each horizon year, a level-of-service analysis shall be performed for the time period(s) that experience the highest degree of network travel. These periods typically occur during the midweek (Tuesday through Thursday) morning (7:00 a.m. to 9:00 a.m.), midweek evening (4:00 p.m. to 6:00 p.m.), and Saturday afternoon (12:00 p.m. to 3:00 p.m.) periods. The transportation impact analysis should always address the weekday a.m. and p.m. peak hours when the proposed lane use action is expected to generate 25 trips or more during the peak time periods. If the applicant can demonstrate that the peak-hour trip generation of the proposed land use action is negligible during one of the two peak study periods and the peak trip generation of the land use action corresponds to the roadway system peak, then only the worst-case study period need be analyzed. Depending on the proposed land use action and the expected trip-generating characteristics of that development, consideration of non-peak travel periods may be appropriate. Examples of land uses that have nontypical trip-generating characteristics include schools, movie theaters, and churches. The roadmaster (or his/her designee) and applicant should discuss the potential for additional study periods prior to the start of the transportation impact analysis.

(9) Traffic Count Requirements. Once the study periods have been determined, turning movement counts should be collected at all study area intersections to determine the base traffic conditions. These turning movement counts should typically be conducted during the weekday (Tuesday through Thursday) between 7:00 and 9:00 a.m. and between 4:00 and 6:00 p.m., depending on the proposed land use. Historical turning movement counts may be used if the data are less than 12 months old, but must be factored to meet the existing traffic conditions.

(10) Trip Generation for the Proposed Development. To determine the impacts of a proposed development on the surrounding transportation network, the trip-generating characteristics of that development must be estimated. Trip-generating characteristics should be obtained from one of the following acceptable sources:

(a) Institute of Transportation Engineers (ITE) Trip Generation Manual (latest edition).

(b) Specific trip generation studies that have been conducted for the particular land use action for the purposes of estimating peak-hour trip-generating characteristics. The roadmaster (or his/her designee) should approve the use of these studies prior to their inclusion in the transportation impact analysis.

(c) In addition to new site-generated trips, several land uses typically generate additional trips that are not added to the adjacent traffic network. These trips include pass-by trips and internal trips and are considered to be separate from the total number of new trips generated by the proposed development. The procedures listed in the most recent version of the Trip Generation Handbook (ITE) should be used to account for pass-by and internal trips.

(11) Trip Distribution. Estimated site-generated traffic from the proposed development should be distributed and assigned on the existing or proposed arterial/collector street network. Trip distribution methods should be based on a reasonable assumption of local travel patterns and the locations of off-site origin/destination points within the site vicinity. Acceptable trip distribution methods should be based on one of the following procedures:

(a) An analysis of local traffic patterns and intersection turning movement counts gathered within the previous 12 months.

(b) A detailed market study specific to the proposed development and surrounding land uses.

(12) Intersection Operation Standards. Crook County evaluates intersection operational performance based on levels of service and “volume-to-capacity” (v/c) ratio. When evaluating the volume-to-capacity ratio, the total traffic demand shall be considered.

(a) Intersection Volume-to-Capacity Analysis. A capacity analysis should be performed at all intersections within the identified study area. The methods identified in the latest edition of the Highway Capacity Manual, published by the Transportation Research Board, are to be used for all intersection capacity calculations. Crook County requires that all intersections within the study area must maintain a v/c ratio of 0.95 or less. It should be noted that the mobility standards in the Oregon Highway Plan apply to Oregon Department of Transportation facilities.

(b) Intersection Levels of Service. Crook County requires all intersections within the study area to maintain an acceptable level of service (LOS) upon full build-out of the proposed land use action. LOS calculations for signalized intersections are based on the average control delay per vehicle, while LOS calculations for unsignalized intersections are based on the average control delay and volume-to-capacity ratio for the worst or critical movement. All LOS calculations should be made using the methods identified in the most recent version of the Highway Capacity Manual (or by field studies), published by the Transportation Research Board. The minimum acceptable level of service for signalized intersections is LOS “D.” The minimum acceptable level of service for all-way stop controlled intersections and roundabouts is LOS “D.” The minimum acceptable level of service for unsignalized two-way stop controlled intersections is LOS “E” or LOS “F” with a v/c ratio of 0.95 or less for the critical movement. Any intersections not operating at these standards will be considered to be unacceptable.

(13) Review Policy and Procedure. The following criteria should be used in reviewing a transportation impact analysis as part of a subdivision or site plan review:

(a) The road system is designed to meet the projected traffic demand at full build-out.

(b) Adequate intersection and stopping sight distance is available at all driveways.

(c) Proposed driveways meet the county’s access spacing standards in Chapter 18.176 CCC, Access Management Standards, or sufficient justification is provided to allow a deviation from the spacing standard.

(d) Opportunities for providing joint or crossover access have been pursued.

(e) The site does not rely upon the surrounding roadway network for internal circulation.

(f) The road system provides adequate access to buildings for residents, visitors, deliveries, emergency vehicles, and garbage collection.

(g) A pedestrian path system is provided that links buildings with parking areas, entrances to the development, open space, recreational facilities, and other community facilities consistent with the requirements of CCC 18.184.010, Pedestrian access and circulation.

(14) Conditions of Approval. In approving an action that requires a traffic impact study, the county may condition approval to ensure that the proposed application will meet operations and safety standards and provide the necessary right-of-way and improvements to develop the future planned transportation system. Conditions of approval may include, but are not limited to:

(a) Crossover easement agreements for all adjoining parcels to facilitate future access between parcels.

(b) Conditional access permits for new developments which have proposed access points that do not meet the designated access spacing policy and/or have the ability to align with opposing access driveways.

(c) Right-of-way dedications for future planned roadway improvements.

(d) Half-street improvements along site frontages that do not have full build-out improvements in place at the time of development. (Ord. 303 § 1 (Exh. C), 2017)