Traffic Access and Impact Study Guidelines & Procedures

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These traffic access and impact study guidelines & procedures define when proposed preliminary subdivision plans and development plans warrant a detailed traffic study and what information should be included in it. All applicants will be required to follow the Planning Commission guidelines and will be treated equally under the same or similar circumstances.

A.   Purpose For Submission Of Traffic Access And Impact Studies

The purpose of performing a traffic impact and access study, as defined by the Institute of Traffic Engineers (ITE), is to:

            1.    provide guidance for short and long range planning of site access;
            2.    provide guidance for on-site circulation and the interface between on-site circulation and
                   off-site traffic;
            3.    provide guidance for off-site improvements needed to permit the roadway system to
                   function satisfactorily so as to accommodate site and non-site traffic;
            4.    assist developers and land owners in making land use site planning decisions regarding
                   traffic;
            5.    identify the contribution a particular development makes to roadway system traffic
                   volumes;
            6.    provide a basis for estimating roadway improvement requirements attributable to a
                   particular project;
            7.    assess the compatibility with local transportation plans (Transportation Element of the
                   Comprehensive Plan);
            8.    enable staff to better evaluate zoning changes and development plans;
            9.    allow appointed and elected officials to know implications of their voting decisions.

B.    Scope Of Required Traffic Access And Impact Studies

    Three (3) levels of study have been identified based on the number of trips that a development is projected to generate in a 24-hour period:

    Level I studies require analysis of each access that the development has to an existing roadway. Access points to be analyzed include public roads, private roads, and non-residential roads. This level of study is commonly required for larger residential subdivisions, office developments, and smaller commercial developments.

    Level II studies require analysis of each access that the development has to an existing roadway, and to the first control point beyond those access points. A control point is an intersection controlled by a traffic signal or stop sign on the existing roadway onto which the development has access. For cases where a traffic control device does not exist, the Planning Commission staff will determine the extent of the study. If an interstate interchange is near the property to be developed and is not signalized, the Planning Commission staff will determine if the ramps need to be included in the study. This level of study is commonly required for moderately sized commercial developments and larger office complexes.

    Level III studies require a complete traffic access and impact study, addressing each access point, the first control point beyond each access point, and the nearest collector/collector intersection or street of higher classification or as determined by the Planning Commission staff. The exact area to be studied will be determined by the Planning Commission staff with input from the study preparer. Level III studies are uncommon, as they are usually warranted only with very large mixed-use and commercial developments.

C.    When Traffic Access And Impact Studies Are Required

    Traffic access and impact studies shall be submitted along with applications for Preliminary Subdivision Plan and Development Plan requests that fall within the following 24 hour trip generation ranges:

    24 Hour Trip Generation            Traffic Study Scope

    750 – 3,000 ADT*                     Level I

    3,001 – 6,000 ADT                    Level II

    6,001 + ADT                             Level III

    * = Cluster Residential Subdivisions with 30 or more lots shall submit at least a Level I study per Item G of this ordinance.

    Trip generation rates for proposed uses shall be calculated using the ITE Trip Generation Manual, 6th (or latest) Edition.

Upon proof by the applicant’s traffic engineer that a lower level traffic impact study would be adequate for a proposed development, or that a traffic impact study is not warranted, the Planning Director may reduce the level of the study or waive the requirement.

D.  Submission And Review Procedures For Traffic Access And Impact Studies

  1. Applicants should conduct a preliminary trip generation assessment of any proposed Preliminary Subdivision Plan or Development Plan to determine if a traffic study will be required. This preliminary assessment should be conducted well in advance of the actual submission of plans.
  2. If the preliminary assessment indicates that a traffic study will be required, the applicant should immediately consult with the Planning Commission staff to verify a development’s projected trip generation, and to confirm whether or not a study will be required. If a study is required, the required level can be determined at that time.
  3. The applicant shall then select a traffic or transportation engineer to prepare the study, who may need to consult with the Planning Commission staff periodically to review the collected data and any assumptions made in the draft report.
  4. Three (3) copies of the completed draft traffic study shall be submitted along with the Preliminary Subdivision Plan or Development Plan application, and all other required materials.
  5. The Planning Commission staff, along with local and state government, shall review the draft traffic study in conjunction with the other elements of the application. If the draft traffic study is not of the proper scope or is executed improperly, the applicant shall be notified of the deficiencies and be required to submit corrections on the same schedule that applies to the other elements of the application. Failure to submit corrections by the posted corrections deadline may lead to an automatic postponement of the application until the next regularly scheduled Planning Commission meeting.

Note: Since a completed traffic study must be submitted at the same time as the application for a development, it is critical that the applicant conduct steps 1-3 early in their planning of a proposed development. Failure to submit a traffic study, or submission of an inadequate study, may lead to a postponement of the application.

E.    Required Qualifications For Preparers Of Traffic Access And Impact Studies

    Traffic access and impact studies shall be prepared under the supervision of a qualified engineer who has specific training in traffic and transportation engineering with experience in preparing traffic studies for existing or proposed developments. The ability to forecast and analyze traffic needs for both developments and the roadway system is essential. All traffic operations and design work shall be completed under the supervision of a registered professional engineer.

F.    Required Specifications For Traffic Access And Impact Studies

  1. Report Requirements – Level I & II Studies
            I.    Introduction
        A.    Description of site including a location map
        B.    Type of project
                                1.    If residential, number and type of dwelling units
                                2.    If commercial, industrial, or office, square footage and type of
                                       development

                    C.    Other planning data that may be pertinent
                    D.    Map of project with proposed access points shown

            II.    Existing Conditions

        A.    Directional traffic counts on roads adjacent to property with access to development

                                1.    Traffic counts shall not be more than one (1) year old

        B.    Level of service of intersection(s), if applicable
            III.    Trip Generation Rates
        A.    Listing of trip generation rates
        B.    Listing of sources for rates used
                1.    ITE Trip Generation, 5th (or latest) Edition
                2.    IF the type of proposed development is not addressed in the ITE
                       Manual, then other rates may be used as long as they are documented
                       and have been approved by the Planning Commission staff.

                    C.    Calculation of trip ends by type of generator

                                1.    Traffic generated by phase
                                2.    100% occupancy and development

            IV.    Trip Distribution

        A.    Assumptions as to the directional distribution of traffic to and from the
                 development.
        B.    Assumptions as the peak hour percentages
        C.    Assumptions as the peak hour directional splits
        D.    Assumptions as the pass-by trips, if applicable (must be approved by the
                 Planning Commission staff).
            V.    Analysis

                        A.    Level of Service (LOS) and capacity analysis for peak periods

                                1.    Compute the projected LOS and capacity analysis for each access point
                                       and control point to the adjacent road system based on the development
                                       by phase.

                                        a.    Highway Capacity Software is recommended (other nationally
                                               recognized software can be used)

                                2.    Compare LOS pre- and post- development, if applicable
                                3.    Link analysis, if applicable

                        B.    Intersection and roadway geometry – existing and proposed

                                1.    Distances from existing streets, driveways, and/or median cuts
                                2.    Alignment with existing streets, driveways, and/or median cuts
                                3.    Intersection layout
                                4.    Sight distance
                                5.    Right-of-way width(s)
                                6.    Lane width(s)

                        C.    Site Circulation
                        D.    Pedestrian facilities

                                1.    Sidewalks
                                2.    School bus stops
                                3.    Transit bus stops, when available

            VI.    Recommendations

                        A.    Site access
                        B.    Intersection improvements

                                1.    Traffic control device(s) – modify existing or need for new
                                2.    Left and/or right turn lanes
                                3.    Acceleration and/or deceleration lanes
                                4.    Length of storage bays

                        C.    Off-site improvements

                                1.    Modification to existing traffic control devices
                                2.    Additional traffic control devices
                                3.    Additional lanes at major intersections
                                4.    Additional roads

                        D.    Improvements by phasing, if applicable

            VII.    Appendix

                        A.    Raw traffic count data
                        B.    Documentation of analysis

    2.    Report Requirements – Level III Studies

In addition to the above noted information, the following, additional information on trip assignment shall be provided in the report prior to the Analysis and Recommendation sections:

            I.    Trip Assignment

                         A.    Show existing ADT’s, proposed development traffic and total traffic for all
                                effected links on the map that identifies the project and the surrounding roads.
                         B.    Show a.m. and p.m. peak hour turning movements for the existing traffic, the
                                proposed development traffic, and the combined traffic at all project entrance
                                intersections, and effected intersections within the study area 
                         C.    Discuss the effects of phasing of the proposed project

G.    Additional Technical Information On Traffic Access And Impact Studies

Additional information of Traffic Access and Impact Studies can be obtained from Traffic Access and Impact Studies for Site Development – A Recommended Practice by ITE.