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Development and Application of a Framework to Classify and Mitigate Truck Bottlenecks to Improve Freight Mobility

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Publication: Transportation Research Record: Journal of the Transportation Research Board
Volume: TRN Annual Meeting
Publication Date: 2018

This paper presents a framework to classify and mitigate roadway bottlenecks and that is designed to improve freight mobility. This is in recognition that roadway operations for trucks are under studied, truck-only bottlenecks are often not identified and freight-specific problem areas are therefore often overlooked. The framework uses four-steps:

Step 1: identifies and locates the roadway sections where vehicle travel time is in excess of what would normally occur.

Step 2: made possible by increasingly available truck probe data, identifies bottlenecks for all vehicles or for trucks only. This is necessary to identify bottlenecks that notably impact freight mobility and might not be identified by car-based approaches.

Step 3: classifies bottlenecks as travel speed-based or process-based. This selects the mitigation treatments as mainly due to operational or roadway limitations.

Step 4: which is the core of the paper, supports the mitigation process by determining the cause of the bottleneck. The bottlenecks are identified as due to congestion, limitations where roadway design slows all vehicles, or where a truck’s size or weight can slow vehicles (such as tight curves or bridge restrictions).

The paper present a review of specific roadway attributes that limit a truck’s mobility and is used to suggest mitigation. The framework is demonstrated using a case study. The framework is designed to be applied by planning and infrastructure agencies who want to locate and address freight bottlenecks in a systematic manner using available resources as well as by researchers interested in linking roadway attributes to truck mobility.

Authors: Dr. Ed McCormackDr. Anne Goodchild, William Eisele, Mark Hallenbeck
Recommended Citation:
McCormack, Edward, Anne Goodchild, W. Eisele, and Mark Hallenbeck. "Development and Application of a Framework to Classify and Mitigate Truck Bottlenecks to Improve Freight Mobility." TRN Annual Meeting, Washington D.C. 2018.

West Seattle Bridge Case Study (Phase I)

West Seattle is an area of the city of Seattle 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 West Seattle to the rest of the city, was closed indefinitely to traffic due to its increasing rate of structural deterioration. Moreover, access to the Spokane Street Lower Bridge, a smaller bridge connecting West Seattle with Harbor Island and the rest of the city, was also restricted; prioritizing heavy freight, public transit, and emergency vehicles. After the bridge closure and restrictions, the total number of vehicle travel lanes crossing the Duwamish River was reduced from 21 to 12.

The unexpected closure of WSHB disrupted passenger and freight mobility to and from West Seattle, increasing travel times and generating bottlenecks on the remaining bridges, which can potentially negatively impact the livability of the peninsula as well as its economy and the environment. The situation might further deteriorate as traffic demand to and from West Seattle increases during recovery from the COVID-19 pandemic.

The Seattle Department of Transportation (SDOT) is taking actions to monitor changes in travel behavior to/from West Seattle and identify and implement strategies that could mitigate the negative impacts caused by the WSHB closure.

SDOT has engaged the Urban Freight Lab to conduct research to explore strategies to alleviate congestion impacts and minimize the disruption of goods and service delivery to West Seattle.

The purpose of this study is to support SDOT to:

  1. understand current freight movements and freight demand in West Seattle;
  2. identify a data-driven mitigation strategy for freight and service flow to and from West Seattle;
  3. assess ex-ante the effectiveness of an implemented strategy.

The freight operations considered and analyzed within the scope of the project are consumer goods and services destined for West Seattle residents and businesses. Intermediate goods and raw materials destined for construction of production and other goods transiting through West Seattle but not destined for local residents or businesses will not be studied.

This project continues with the West Seattle Bridge Case Study Phase II.

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

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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. 
Technical Report

Defining Washington State Truck Intermodal Network

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Publication: Washington State Transportation Center (TRAC)
Publication Date: 2011

In order to support WSDOT in development of the Washington State Freight Mobility Plan, this document presents recommendations for criteria to be used in defining the Washington state truck intermodal network.

The state does not have an existing definition of the freight truck-intermodal system. To establish the criteria, this project reviewed methods used by other states, identified the facilities in Washington specified by the National Highway System, and compared these facilities to those identified by regional planning organizations. Finally, recommendations are made for criteria to use in identifying the truck intermodal network for Washington.

Recommended Citation:
Goodchild, A. V., & Ivanov, B. (2011). Defining the Washington State Truck Intermodal Network (No. WA-RD 783.1). Washington State Department of Transportation, Office of Research & Library Services.