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West Seattle Bridge Case Study (Phase II)

Start Date: January 2022
Funding: City of Seattle Department of Transportation (SDOT)
Project Budget: $60,000
Principal Investigator(s): Dr. Anne Goodchild
Project Manager(s): Dr. Giacomo Dalla Chiara

This project is a continuation of the West Seattle Bridge Case Study Phase I.

West Seattle (WS) is an area of the city of Seattle, Washington, located on a peninsula west of the Duwamish waterway and east of the Puget Sound. In March 2020, the West Seattle High Bridge (WSHB), the main bridge connecting WS to the rest of the city, was closed to traffic due to its increasing rate of structural deterioration.

The Seattle Department of Transportation (SDOT) has engaged the Supply Chain Transportation and Logistics Center (SCTL) at the University of Washington, to conduct research to understand current freight movements and freight demands in WS and identify challenges related to the bridge closure to inform data-driven mitigation strategies.

In project Phase 1 the research team performed a freight trip generation (FTG) estimation and conducted interviews with local business establishments, carriers, and the Port of Seattle. As a result of the FTG modeling, the research team estimated that 94 percent of the freight trips generated by WS are destined to residential buildings. Moreover, the interviews identified disruptions in the supply chains of small and medium-size local businesses as well as carriers facing longer travel times to access the peninsula.

Research Objectives: 
In Phase 2 of the project, the research team will shift the focus from business establishments to consumers. In particular, we will explore consumer behavior, defined as how people choose to buy goods and services and where they buy them, to better understand residential demand and accessibility of goods for WS residents.

This study will make use of a consumer survey for Seattle residents to:

  • Describe consumer behavior and buying habits for Seattle residents, in particular, we will address how (online vs. in-person and with which travel mode), where (locally or not-locally), and how often people shop.
  • Better understand what drives consumer behavior, in particular how consumer behavior is impacted by urban form (transport infrastructure available, land uses, urban density, etc.), access to transportation, local access to stores, and socioeconomic characteristics.


  1. Gather public datasets and review previous consumer surveys: The research team will review and summarize publicly available datasets that contain information on consumer behaviors and urban form for Seattle residents, for instance, the Puget Sound Regional Council (PSRC) data, the National Household Travel Survey (NHTS), the Freight Trip Generation (FTG) estimates from Phase 1, the Google Maps APIs and the publicly available Seattle Department of Transportation (SDOT) GIS layers. The research team will also scan the scientific literature and reports to inform the design of the survey on consumer behavior.
  2. Survey Design: The research team will design a consumer survey and a method of survey distribution. The survey will include socioeconomic data (e.g. age, gender, income, education, household composition, car ownership), geographical location (where the interviewee lives), consumer behavior (e.g. types of goods purchased, the amount spent, where goods are purchased, mode of travel, whether goods were purchased online or in-person, how often the purchases take place). SDOT will be provided the opportunity to review and give comments on the draft survey before the survey roll-out.
  3. Survey roll-out: The approved survey will be distributed to residents of the agreed study area. The survey will be drafted as an online survey. SDOT will reserve the option to further expand the survey reach, for instance by creating and distributing a paper version of the survey, translating the survey to other languages, use SDOT channels to distribute the survey.
  4. Analysis of survey data: Data from the survey will be analyzed. A descriptive statistical analysis will be performed, addressing questions such as how people consume, how far people travel to purchase goods, what is the preferred mode of transportation for shopping trips, and how frequently people purchase things online vs. in person. A second part of the analysis will focus on understanding the relationship between socioeconomic variables and urban form variables with consumer behavior variables.
  5. Reporting: A final report will be drafted reporting on the survey design and method, a data description, and data analysis addressing the project goals. SDOT will review and confirm the final report before publication on the SCTL website.

Deliverables: Final project report and executive summary

Budget: $60,000
Timeline: January to December 2022