What Methodologies and Parameters Must Be Followed in Doing the Analysis?

  1. All Transportation Impact Analyses must include a statement by the engineer that the resulting transportation network with the development and mitigation measures as proposed will provide adequate facilities for the public that meet all appropriate safety standards and practices.
  2. For any County Roads or State Highways (including interchange areas) within or adjacent to the study area, the analysis must meet the requirements of the appropriate County and/or the Oregon Department of Transportation.  Contact the appropriate agency for their requirements.
  3. Traffic counts, delay studies, and other on-site analysis must be done during normal or reasonable worst-case traffic conditions within 12 months of the analysis date.  This is typically on a Tuesday, Wednesday, or Thursday (except for weekend scenarios) in decent weather with school in session and no unusual events/holidays that would affect traffic.
  4. The Level of Service (LOS), Volume/Capacity Ratio (V/C), and other analysis parameters for existing conditions must be calibrated to on-site conditions through delay studies and other measurements.  Calculation methods must match actual on-site conditions based on the procedures in the current Highway Capacity Manual approved by ODOT and other accepted standards, and a description of this calibration process and resulting adjustments must be included in the analysis report.
  5. Per Tualatin Development Code Chapter 74 Intersections should be improved to operate at a level of service of at least D and E for signalized and un-signalized intersections, respectively.
  6. Acceptable analysis methods and software include the current ODOT approved Highway Capacity Manual methodology, ITE Trip Generation Manual, Synchro, SimTraffic, Vissim, Vistro, SIDRA Intersection, MUTCD, AASHTO, and other commonly accepted traffic analysis programs.  Check with City staff beforehand to verify the acceptability of a particular method if in question.
  7. Signal timing used in capacity or progression analysis shall be within the signal timing parameters currently used at that location.  Adequate time must be provided for pedestrian crossing at crosswalks at MUTCD crossing rates.  Any assumptions about progression must match existing conditions and/or be approved by the agency timing the subject traffic signals.  New crosswalk closures are typically not permitted.  Signal timing alone is not an acceptable mitigation measure.
  8. All calculations, analysis results, and conclusions must be reasonable, understandable, consistent, and fully explained.  Conclusions must be consistent with the analysis presented.  Calculations, graphs, tables, data, results, and/or conclusions that are contrary to engineering practice and/or common sense will not be accepted and may lead to the traffic study being returned to the applicant for correction.
  9. If the development proposal changes in ways that, in City staff’s judgement, would materially affect the traffic study, the traffic study must be revised or re-done to account for such changes.
  10. The attached checklist will be used by City staff to determine if a Transportation Impact Analysis contains sufficient information to be reviewed.  Acceptance for review does not signify adequacy, and changes may be required in the review process.  Incomplete and/or unacceptable analyses will be returned for completion/correction.
  11. Cooperation between the applicant, the applicant’s engineer, and City staff is strongly encouraged throughout this process.  Please do not hesitate to contact City staff with any questions.
Microsite: 
Engineering
Category: 
Tualatin Traffic Study Requirements
FAQ Weight: 
7.00
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