1. Purpose.
A. To allow Story County to determine the safety and congestion impacts, and related consequences, of proposed major traffic generating uses;
B. To require that applicants respond with reasonable proposals to resolve potential negative traffic impacts that their proposed uses will have on the county and other nearby streets;
C. To recognize that sufficient federal, state and county funds are not always available to resolve traffic issues caused by private development;
D. To assist in carrying out Chapter 5, Land Use, and Chapter 7, Transportation, of the Story County Cornerstone to Capstone (C2C) Comprehensive Plan and the Story County Land Development Regulations;
(Ord. 317 – Apr. 24 Supp.)
E. To ensure that county roads bordering a subdivision or land development are coordinated and of such widths, grades, and surface types and in such locations as deemed necessary to accommodate proposed traffic and to facilitate adequate safety protection;
F. To assist the Story County Engineer in evaluating existing county roads in the vicinity of proposed subdivisions and other land development for traffic levels, future capacity, road conditions, and needed transportation improvements;
G. To ensure that the access into and out of subdivisions and other land developments is reasonably safe; and
H. To assist in assuring all new transportation systems will be compatible with the existing county transportation network to promote efficiency and safety.
2. Administration.
A. A Traffic Impact Analysis is required for all proposed commercial or industrial development (as defined in Chapter 88.01 General Regulations) including those requiring a conditional use permit and for major residential subdivisions (as defined in Chapter 87.09 Major Subdivision Plats) when a proposed development will generate equal to or greater than 100 new vehicle trips per day. The Traffic Impact Analysis shall be submitted with the application. The Story County Engineer may require a Traffic Impact Analysis when less than 100 new vehicle trips per day will be generated if there are safety or roadway/intersection capacity deficiencies or when two or more proposed developments will generate equal to or greater than 100 new vehicle trips per day.
B. A Traffic Impact Study may be required by the Story County Engineer, Board of Supervisors, or Board of Adjustment, based on the results of the traffic impact analysis, including impacts of the development on roadway and intersection operating conditions, levels of service, or due to a high incidence of accidents. If required, the traffic impact study shall be submitted prior to consideration by the Board of Supervisors or Board of Adjustment.
C. The Traffic Impact Analysis and/or Traffic Impact Study shall be prepared by an Iowa licensed professional engineer with expertise in the preparation of traffic impact studies.
D. The full cost of the Traffic Impact Analysis and/or Traffic Impact Study shall be the applicant's expense.
E. Proposed improvements identified in the Traffic Impact Analysis and/or Traffic Impact Study shall be reviewed and evaluated by the Story County Engineer and Board of Supervisors and may be included as a county project with the annual adoption of the Story County Capital Improvements Plan and budget at the discretion of the Board of Supervisors.
F. The county may require traffic improvements, including dust control, within or nearby the site to be provided by the applicant, as recommended by the Story County Engineer to the Board of Supervisors, as a specific condition of approval to be paid at the applicant's expense, based on the Traffic Impact Analysis and/or Traffic Impact Study.
G. Joint traffic studies between different applicants for related projects are acceptable and are encouraged. When a development is proposed in an area where a Traffic Impact Analysis or Study has been previously completed, Planning and Development staff shall provide the previous analyses and studies to the applicant and/or their engineer. The previous analyses/studies shall be considered as part of the development's Traffic Impact Analysis or Study.
H. If phased development is proposed, the Traffic Impact Analysis and/or Traffic Impact Study shall include projections for traffic that will be generated by all phases of development at its completion.
3. Contents of the Traffic Impact Analysis.
A. The following information shall be required as part of the Traffic Impact Analysis.
(1) The analysis shall describe the proposed development, existing land use, and adjacent land uses.
(2) The analysis shall show the site location, study area boundary, and other approved and pending developments within the study area. The study area shall include all county roads and intersections within a radius of one-half mile of the site or the nearest major intersection(s) after which the impact of the development is no longer discernible, whichever is greater.
(3) The analysis shall determine the existing number of vehicle trips per day and during typical peak hours on county and public streets within the study area.
(4) The analysis shall determine the number of vehicle trips per day and during typical peak hours generated by the proposed development. Trip generation rates shall be based on most recent edition of the Institute of Traffic Engineers (ITE) Trip Generation Manual or other professionally accepted source.
(5) The analysis shall determine if the existing street conditions and intersections within the study area are adequate and provide safe access and any potential impacts on existing operating conditions, including level of service.
(6) The analysis shall provide crash data for all intersections within the study area for the past 10 years, as applicable.
4. Contents of the Traffic Impact Study.
A. The following information shall be required as part of the Traffic Impact Study. The study shall include a pedestrian safety analysis, and, where appropriate, proposed traffic calming measures. The study area shall include all county and public streets and intersections within a radius of one-half mile of the site or the nearest major intersection(s) after which the impact of the development is no longer discernible, whichever is greater, unless the Story County Board of Supervisors and/or the Story County Engineer determines other parameters to include in the study. Trip generation rates shall be based on most recent edition of the Institute of Traffic Engineers (ITE) Trip Generation Manual or other professionally accepted source.
(1) Current and peak hour Average Daily Trips (ADT) and peak hour volumes of streets adjacent to any proposed publicly dedicated streets, intersections, or access drives,
(2) Projected ADT of the development,
(3) Projected peak AM, PM, and/or weekend traffic volumes of the development,
(4) Existing and proposed level of service (LOS), as defined by the Transportation Research Board Highway Capacity manual (most recent edition), of proposed publicly dedicated and existing public streets and intersections within the development and study area,
(5) Modal split of services (categories of vehicles) traveling to and from the site,
(6) Proposed sight distances at the intersections of existing and proposed publicly dedicated streets, intersections, and/or access drives,
(7) Existing and proposed pedestrian paths from streets and within the site to entrances of all buildings, where applicable,
(8) Site traffic distribution or the direction vehicles will take to access or leave the project site,
(9) Site traffic assignment or the actual routes taken to and from the site,
(10) Projected ADT and peak hour volumes of all streets and intersections within the development and study area,
(11) An assessment of the change in roadway operating conditions within the study area resulting from the development traffic,
(12) Proposed facilities to accommodate mass transit and bicycle access to site, and
(13) How the development and its access(es) or operation is consistent with comprehensive and/or transportation plans for the study area.
B. It shall also identify improvements/facilities to be installed or actions to be undertaken to ensure the following:
(1) LOS C or higher overall for all new publicly dedicated streets, intersections, and access drives,
(2) No reduction in the levels of service for existing street, intersections, and access drives, except that LOS D shall be permitted during the AM and PM peak hour,
(3) Sight distances for all new publicly dedicated streets and access drives intersecting with all existing streets shall meet Story County and/or Iowa DOT requirements as applicable,
(4) If pedestrian paths cross vehicular drives and parking areas within the site, adequate measures to ensure pedestrian safety,
(5) Provision of safe pedestrian and bicycle access, and, if feasible, mass transit to the site,
(6) Where appropriate, effective traffic calming measures should be outlined,
(7) No reduction in the LOS of intersections within the study area as a result of the development; however, if the intersection already has an LOS F, no reduction in the intersection delay shall occur,
(8) Where high incidence of accidents for any adjacent intersection exists, safe sight distances, adequate traffic control restrictions, and safe pedestrian crossings for each adjacent impacted intersection,
(9) If any proposed intersection or access drive is within one-fourth mile of the property line of any public or private elementary or secondary school, safe pedestrian crossings for all intersections and access drives are provided, and
(10) If pedestrian paths cross vehicular drives within the development, adequate points of pedestrian right of-way and traffic flow restrictions as necessary to ensure pedestrian safety.