Traffic Impact Analysis

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A traffic impact analysis or traffic report is a study of the potential traffic impacts of a development on the surrounding transportation system. The purpose of the study is to document the impacts and recommend on-site and off-site mitigation for those impacts.

A traffic report is required for any new development, redevelopment or change of use (including tenant improvements).

The applicant will hire a consultant to provide the traffic report. The consultant must be a professional engineer, licensed in Washington. There are two types of traffic reports.

Level-One Traffic Report

Level-One Traffic Reports are required for all new development, redevelopment or change of use projects. Some of the items to be included in the report are:

  1. Project Narrative
    • Existing and Proposed Use
    • Existing and Proposed Access Design
    • Existing Traffic Standard Nonconformities
  2. Trip Generation Data
    • Existing
    • Proposed Project Trips
    • Net New Trips
  3. Sight Distance for Vehicles and Pedestrians
  4. Other Information, as needed
  5. Recommendations
  6. Conclusions

Level-Two Traffic Report

Level-Two Traffic Reports are required for larger, more complex projects. Some of the items to be included in the report are:

  1. All Level-One Traffic Report Requirements as noted above
  2. Vicinity Map
  3. Discussion of internal circulation; may include a queuing analysis and loading plan with turning exhibits
  4. Concurrency
  5. Trip Distribution
  6. Level of Service
  7. Discussion of pedestrian, bicycle, and transit facilities
  8. Accident Report Data
  9. On-site and Off-site Mitigation
  10. Traffic Management Program