- Purpose. To establish requirements and provide criteria for site-development traffic impact studies.
- Authority. The authority to promulgate these Troutdale Administrative Rules pertaining to traffic impact studies is contained in Section 2.040 B of the Troutdale Development Code.
- When Required. A site-development traffic impact study conforming to these Troutdale Administrative Rules is required with the development’s land use application (or building permit application if no land use application is involved) if the proposed development is expected to generate more than 1,000 vehicle trips per weekday or if, in the judgment of the Director, the proposed development’s location, site plan, or trip generation characteristics could adversely affect traffic safety, access management, or street capacity, or aggravate other known traffic deficiencies in the vicinity.
- Who Performs. The traffic impact study shall be performed by a Professional Engineer competent in traffic engineering and registered in the State of Oregon or a Traffic Engineer registered in the State of Oregon.
- Elements of the Study. The traffic impact study shall contain the following elements, as a minimum:
- Purpose and Objective. Describe the purpose of the study, key traffic issues to be addressed, the characteristics of the surrounding transportation system, and the development objectives related to the proposed site.
- Project Description. Describe the existing land uses and proposed land uses, including a map showing the site plan and all vehicle access points onto a roadway. Provide an estimated time line for full development of the site.
- Existing Conditions. Describe surrounding roadway facilities, including their functional classification, the nature and intensity of nearby pedestrian and bicycle facilities and activity, and current or planned transit routes. Analyze the level of service of key study intersections and/or arterial corridors as proposed by the Engineer and approved by the Director, including roadnet diagrams with percentage distributions and resulting traffic volumes and traffic control devices. (In general, key study intersections include any intersection which will be impacted by 10 or more site-generated trips during the weekday p.m. peak hour.)
- Background Conditions. Analyze the level of service for background traffic conditions, which are the future non-site-related traffic volumes during the future year when the proposed site is expected to be fully developed. Background conditions also include approved but not yet completed off-site developments within the study area. Utilize the same intersections and/or arterial corridors as used for Existing Conditions and include similar diagrams.
- Site-Generated Conditions. Provide expected site-generated trips, trip assignment, and modal split. The trip generation estimate should utilize the latest edition of the Institute of Transportation Engineers “Trip Generation Manual” unless more appropriate data is available, assuming full build-out of the proposed development. Utilize the same intersections and/or arterial corridors as used for Existing Conditions and include similar diagrams. The trip distribution methodology can be based on trip patterns of similar nearby developments, existing intersection or corridor volumes, modeling results from Metro, and/or the anticipated market area of the proposed development. The selected methodology is subject to approval by the Director.
- Total Conditions. Analyze the level of service at the same key study intersections and/or arterial corridors as used for Existing Conditions for total (background plus site generated) conditions. Include similar diagrams.
- On-Site Circulation. Describe on-site circulation for all transportation modes, identify any potential turning-movement conflicts or unsafe queuing hazards, and propose solutions thereto.
- Summary. Summarize key findings of the study and recommendations to mitigate deficiencies.
