Transportation Engineering Northwest

Transportation Impact Studies Traffic Engineering/Operations
Design Services Planning/Demand Forecasting
Traffic Impact/Operations

We are thoroughly familiar with SEPA (Washington State Environmental Policy Act) and NEPA (National Environmental Policy Act) guidelines and requirements, and have conducted numerous traffic impact analyses under the Washington State Growth Management (GMA) legislation. Our staff has provided expert witness testimony for hearings before hearing examiners, citizen review boards, elected officials, and in state courts. We have prepared and successfully defended transportation impact studies for a variety of private developments and several controversial projects.

One of our greatest strengths in transportation impact analysis has been our ability to evaluate a wide range of “non-traditional” land use proposals in the context of SEPA and NEPA review. Many of our projects have involved user-specific trip generation studies and national research to provide our clients with a substantial and defensible basis to evaluate environmental impacts.

The adequacy of on-site parking supply and potential off-site overflow has been an issue on many of our past projects. We have worked with developers,

local agencies and community groups to achieve a reasonable balance between parking supply and demand, as well as ways to mitigate overflow on peak demand days or periods.

TENW employs a variety of innovative and specialized tools to evaluate complex transportation systems involving both roadways and intersections. Various transportation simulation models and software programs are used by TENW staff to evaluate transportation impacts, identify problems, and provide innovative solutions.


Some of the many projects TENW has recently completed include the following:

  • Hawks Prairie Park and Ride: Award Winner – Lacey, Washington
  • Swedish Hospital Medical Centers – Issaquah, Redmond and Snohomish County, Washington
  • Boeing Renton Comprehensive Plan Amendment EIS (2004 PRSC Vision 2020 Award) – Renton, Washington
  • Redmond High School Addition – Redmond, Washington
  • Tuscan Village Resort Community – Chelan, Washington
  • Cascade Casino & PTOI Civic Facilities – Tacoma, Washington
  • Bravern (Mixed Use) – Bellevue, Washington
  • WSU Bonney Lake Demonstration Forest EIS – Bonney Lake, Washington
  • Tukwila South EIS – Tukwila, Washington