Traffic Impact Assessment Requirements

When conducting a traffic impact assessment, the first thing to look for is the TIA requirements and guidelines of the authority that regulates the road network adjacent to your subject development. Every City, County, Municipality, Town, or even Highway authority has its own guidelines that determine the composition of the report. Some authorities do not even require TIA reports at all, while others have defined thresholds for when a Traffic Impact Assessment is required. These thresholds are usually based on development size or the expected number of cars using it. Click here to learn about the purpose of a Traffic impact assessment before you start your analysis.

Before you begin your analysis, make sure you have all the following tools and information readily available:

Tools and Software for Traffic Impact Assessments

  1. ITE Trip Generation Manual: Obtained from the Institute of Transportation Engineers website;
  2. Information of Local Traffic Directional Distribution Patterns and Transportation Mode Share: Obtainable through a transportation survey or engineering judgement;
  3. Traffic analysis software (Synchro/Vissim/Vistro/Arcady/Sidra): Purchased from the software creator for Intersection Capacity Analysis;
  4. AutoCAD Sofware with the AutoTURN plugin installed: To conduct vehicle circulation analysis; and
  5. Microsoft Office Tools, especially MS Excel, and MS Word.
Traffic Impact Assessment Requirements
Intersection Capacity Analysis is a major component of Traffic Impact Assessments

Development Related Information

  1. Complete Site Plan and Statistics in PDF and AutoCAD drawing formats: Provided by the developer;
  2. Anticipated Construction and Occupancy year of the proposed development: Indicated by the developer.
  3. Developer’s Intention to pay for road improvements and implement transportation demand management strategies.

Study Area Particulars

  1. Traffic Impact Assessment Requirements for your jurisdiction – Obtainable from the road authority;
  2. Road Network Data including:
    • Intersection Layouts including lane markings and intersection controls: Can be obtained using google satellite imagery;
    • Signal Timing Plans of Signalized Study Intersections: Obtainable from the road authority;
    • Recent Existing Traffic Volume Counts on Study Intersections: Obtained through a traffic count survey or the road authority;
  3. Background (nearby) Development Information (Available through TIA Reports of other Approved Developments): Obtained from Internet search or the Road approval Authority;
  4. Traffic Growth rate: Derived through historical traffic counts, population growth, other traffic impact assessment reports, TIA guidelines, or a value agreed upon with the authority.
  5. Applicable Zoning by-laws regarding Parking, Loading, and Traffic Safety: Available from the road authority.
Traffic Impact Assessment Requirements - Geometry
Use satellite imagery to obtain Intersection Geometry including Approaches Lanes. and Pavement Markings

In addition to these requirements, a pre-study discussion with the developer and the approval authority is necessary to ensure everyone is on the same page and if we should consider any other factors.

Who can prepare a traffic impact Assessment

Technically, anybody with good analytical, software, and technical report writing skills is competent enough to conduct a traffic impact assessment. However, some jurisdiction guidelines state that traffic impact assessments must be prepared by a registered engineer or planner. In some cases, traffic impact assessments reports must be signed and stamped by a licensed Professional Engineer or Registered Professional Planner.

Usually, engineering consulting firms undertake these assignments for private developers since they possess the qualified staff and specialized traffic analysis software licenses. It is important to use software recognized by the approval authorities as they may ask for the analysis files to conduct their own review of your work.

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