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Freight and Transit Lane Study (Task Order 7)

The City of Seattle Department of Transportation (SDOT) engaged the Urban Freight Lab to conduct research on the impacts of a Freight and Transit-Only (FAT) Lane in place in January 2019. The research findings will be used to understand the FAT Lane’s performance towards achieving city goals and to guide the development of future FAT Lane projects.

The Seattle Freight Master Plan includes a FAT Lane strategy to reach the city’s economic goals:

  • (2) Economy – Provide a freight network that supports a thriving and diverse economy for Seattle and the region.
  • (2.4) Maintain and improve truck freight mobility and access between and within the city’s MICs and to the regional highway system
  • (2.4.2) Explore and test the use of truck-only lanes to improve freight mobility on city streets with high truck volumes

SDOT’s key research interests in this project are to:

  1. Document whether the FAT Lane’s benefits to truck drivers were strong enough to attract heavy freight vehicles from using other downtown streets. This will be measured by comparing truck volume on the Lane during implementation to volume after it was closed.
  2. Determine whether passenger cars followed the posted FAT Lane restrictions. This will be measured by documenting the number of cars violating the rule.
  3. Document transit use during the implementation period.


The Alaskan Way Viaduct, a major freight thoroughfare in Seattle, was closed on January 11, 2019 significantly reducing capacity in the already congested road network in Greater Downtown Seattle. To improve freight and transit access to commercial and industrial areas in the city, the City of Seattle Department of Transportation, in partnership with the WSDOT, temporarily installed two blocks of a Freight and Transit Lane on Alaskan Way.

The FAT Lane was in the curb lane only, on southbound Alaskan Way (at street level, not on the Viaduct). The 2-block segment is north of Little H on Alaskan Way, which provides access to Colorado and Alaskan Way. The FAT Lane supported Port of Seattle operations.

Research Tasks:

The following tasks will be completed by the Urban Freight Lab:

Task 1 – Research Scan


  1. Conduct a short research scan of published reports that provide data-based evidence of the results of FAT Lane projects.
  2. Write a 2-3 page summary of the results of other FAT Lane projects

Task 2 – Analysis of video data


  1. SDOT will provide video of the FAT Lane segment taken when the Lane was open and after it closed, to the UFL. The UFL will categorize and count vehicles in the lane as follows:
    • Transit/bus
    • Passenger/car
    • Truck/freight:
      1. Drayage with container
      2. Drayage without container
      3. All other trucks/freight vehicles. This category includes: delivery vans/trucks, construction and waste vehicles, and if readily apparent service commercial vehicles.
    • Other vehicles, e.g. those lacking differentiating features to categorize.
  2. UFL will analyze the count data and include key findings in the final report. The analysis will include:
    1. A comparison of truck volume on the Lane during implementation to the volume after it was closed. This may include time of day, day of week, or other factors.
    2. The number of passenger cars in the Lane during implementation. e.g. the number of violators.
    3. The UFL researchers will also explore whether comparing data collected in the Greater Downtown Cordon study to data collected in this study yields valid findings.
Technical Report

Freight and Transit Lane Case Study

Download PDF  (3.57 MB)
Publication Date: 2020

The Seattle Department of Transportation (SDOT) engaged the Urban Freight Lab at the Supply Chain Transportation and Logistics Center at the University of Washington to conduct research on the impacts of a freight and transit (FAT) lane that was implemented in January 2019 in Seattle. To improve freight mobility in the City of Seattle and realize the objectives included in the city’s Freight Master Plan (FMP), the FAT lane was opened upon the closing of the Alaskan Way Viaduct.

The objective of this study was therefore to evaluate the performance and utilization of the FAT lane. Street camera video recordings from two separate intersection locations were used for this research.

Vehicles were categorized into ten different groups, including drayage with container and drayage without container, to capture their different behavior. Drayage vehicles are vehicles transporting cargo to a warehouse or to another port. Human data reducers used street camera videos to count vehicles in those ten designated groups.

The results of the traffic volume analysis showed that transit vehicles chose the FAT lane over the general purpose lane at ratios of higher than 90 percent. By the time of day, transit vehicle volumes in the FAT lane followed a different pattern than freight vehicles. Transit vehicle volumes peaked around afternoon rush hours, but freight activity decreased during that same time. Some freight vehicles used the FAT lane, but their ratio in the FAT lane decreased when bus volumes increased. The ratio of unauthorized vehicles in the FAT lane increased during congestion.

Further analysis described in this report included a multinomial logistic regression model to estimate the factors influencing the choice of FAT lane over the regular lane. The results showed that lane choice was dependent on the day of week, time of day, vehicle type, and location features. Density, as a measure of congestion, was found to be statistically insignificant for the model.

Recommended Citation:
Urban Freight Lab (2020). Freight and Transit Lane Case Study.