All posts by trac

Right Sizing Low Impact Development (LID) Best Management Practices (BMPs) to Aid in Reducing 6PPD in Stormwater Runoff

Low impact development (LID) best management practices (BMPs) may aim to treat roadway runoff near its source through dispersion and infiltration. These BMPs are crucial for reducing chemicals such as 6PPD and 6PPD-q, which derive from tire preservatives and have been linked to high mortality rates in coho salmon. Unfortunately, WSDOT’s current methods for estimating runoff infiltration rates is believed to be overly conservative, rendering the LID BMPs infeasible and substantially increasing runoff mitigation costs. Runoff infiltration rate is the product of saturated hydraulic conductivity and the hydraulic gradient. The goal of this research is to refine the method WSDOT uses to estimate hydraulic gradients, enabling it to produce more accurate and less conservative estimates of infiltration rates. These refinements should help improve the feasibility, cost-efficiency, and environmental effectiveness of LID BMPs used in WSDOT stormwater designs. This in turn should encourage broader adoption of LID BMPs and help reduce 6PPD-related environmental impacts, particularly in fish-sensitive areas.

Principal Investigators:
Brett Mauer
Mike Gomez
Pedro Arduino
Civil and Environmental Engineering, UW

Sponsor: WSDOT
WSDOT Technical Monitor: Rani Jaafar
WSDOT Project Coordinator: Mustafa Mohamedali
Scheduled completion: May 2027

Laser Scanner Data Collection to Refine Chip Seal Construction Specification

Approximately 7,000 miles of Washington state roadway are paved with chip seals. Chip seals cost less than hot mix asphalt projects and can extend the life of asphalt pavements. The chip embedment depth, or the percentage of chips embedded in the asphalt, plays a crucial role in determining the seal’s performance. Improper chip embedment can lead to raveling, flushing, and bleeding. Unfortunately, there are no specifications governing the required percentage of embedded chips, nor are there data-driven methods available to measure chip embedment depth during construction. In a previous project, the researchers demonstrated the successful use of a laser texture scanner to measure chip embedment depth, and they developed a draft specification for it. This project is collecting field performance data for chip seals that were constructed in 2022 and measured as part of that previous study. With those data the researchers will refine the specification and acceptance criteria for chip seals based on percentage of embedment to be included in the WSDOT Construction Specifications. The resulting specification and measurement method should allow WSDOT to apply chip seals more successfully and cost effectively.

Principle Investigator: Haifang Wen, Civil and Environmental Engineering, UW
Sponsor: WSDOT
WSDOT Technical Monitor: Riley Bender
WSDOT Project Coordinator: Shervin Jahangirnejad
Scheduled completion: June 2027

Collaborative Research: Fostering Collective Rationality Among Self-Interested Agents to Improve the Design and Efficiency of Mixed Autonomy Networks and Infrastructure Systems

This Early-Concept Grants for Exploratory Research (EAGER) project is investigating the emergence, mechanisms, and applications of collective rationality among self-interested vehicle agents in the design of mixed autonomy transportation networks and infrastructure systems. Collective rationality refers to the ability of self-interested members of a group to make consistent, logical decisions that maximize overall, shared benefits. This project will explore and rigorously define the concept of collective rationality in the context of mixed traffic and will explore its application to designing the strategic behaviors of autonomous driving agents in mixed autonomy transportation systems. The core hypothesis is that collective rationality can emerge in broad scenarios even if the involved agents are self-interested. The researchers are leveraging game theory and reinforcement learning to verify this hypothesis theoretically and computationally. The results may help reduce travel cost, uncertainties, and fuel emissions, as well as enhance equity among all road users. Broader applications may include autonomous vehicle behavior design and emergency evacuation.

Principle Investigators:
Jia Li, Civil and Environmental Engineering, WSU
Michael Zhang, Civil and Environmental Engineering, UC Davis

Sponsor: National Science Foundation
Scheduled completion: August 2026

Bridging the Gap: Identifying and Addressing Active Transportation Disparities in Underserved Rural Residential Clusters 

Residents of rural residential clusters (RRCs) in Washington often face systemic barriers to safe, affordable, and reliable transportation, resulting in disproportionate hardship and limited access to essential services. The goal of this study is to advance transportation equity by identifying, analyzing, and addressing active transportation (AT) disparities in transportation-disadvantaged RRCs. For this research, an RRC is defined as a small, unincorporated cluster of adjacent homes located along a state highway or major county road. The study area encompasses nine counties in western Washington state, extending from Lewis County northward to the Canadian border. For this project, the researchers are developing a geospatial method for identifying and mapping state and major county roads that prevent residents of RRCs from using AT. They are assessing the specific AT needs, challenges, and perceptions of residents in these communities and are identifying the kinds of infrastructure improvements that would be responsive to local priorities and experiences. They are also developing resources and tools—including a geospatial database, prioritization methodology, and reproducible workflow—to support targeted interventions that WSDOT can implement to improve connectivity, safety, and equitable access for residents of RRCs across the state.

Principal Investigators:
Angela Kitali
Jeff Walters
School of Engineering and Technology, UW Tacoma

Sponsor: WSDOT

WSDOT Technical Monitors:
Grace Young
Brian Wood

WSDOT Project Coordinator: David Strich
Scheduled completion: February 2027

Shore Power: Partnerships to Provide eMobility Options at the Bremerton Ferry Terminal for a Greener Future

Washington State Ferries (WSF) has prioritized electrification as a core strategy to reduce greenhouse gas emissions, improve accessibility, and alleviate congestion at key terminals. This project aims to develop a replicable interagency planning framework for integrating electrified mobility options at ferry terminals. Integrating electric mobility (eMobility) solutions requires a comprehensive approach that includes expanding access to transit, enhancing multimodal travel options, and deploying electrification infrastructure. The Bremerton Ferry Terminal provides a unique opportunity for electrification, given its role as a regional transportation hub with direct connections to Seattle. For this project, researchers are analyzing current mobility challenges, evaluating eMobility and electrification solutions, performing cost analysis and energy demand modeling, creating a scalable planning framework, and engaging stakeholders and facilitating knowledge transfer among WSF, Kitsap Transit, utility providers, and local agencies. The results will support Washington state’s transition to a more resilient, efficient, and equitable transportation system.

Principal Investigators:
Hyun Woo “Chris” Lee, Construction Management, UW
Rachel Berney, Urban Design and Planning, UW
Lingzi Wu, Construction Management, UW
Bart Treece, Mobility Innovation Center

Sponsor: WSDOT
WSDOT Technical Monitor: Kevin Bartoy
WSDOT Project Manager: Mustafa Mohamedali
Scheduled completion: June 2027

Seismic Collapse Prevention for WSDOT Bridges

Earthquakes threaten the functionality and safety of the highway transportation system in Washington state. Given the state’s funding constraints, WSDOT needs to focus scarce resources on the bridge failure mode that is most likely to lead to bridge collapse, namely the shear failure of reinforced concrete columns, and the bridges that are most likely to suffer from column shear failures. This project is developing a new methodology, or modifying an existing one, to evaluate the seismic-shear vulnerability of WSDOT bridges with reinforced-concrete columns.  This will allow WSDOT to account for the amount of shear-strength reduction that will result from repeated cycling during long-duration and shorter-duration earthquakes. The researchers will also provide WSDOT with the practical tools and training needed to implement the developed methodology. The results should enable more reliable characterization of post-earthquake transportation functionality, which will support improved emergency planning. 

Principal Investigators:
Marc Eberhard, Civil and Environmental Engineering, UW
Jeffrey Berman, Civil and Environmental Engineering, UW

Sponsor: WSDOT
WSDOT Technical Monitor: Amy Leland
WSDOT Project Manager: Mustafa Mohamedali
Scheduled completion: October 2027

Sound Mitigation Study of the SR 520 Bridge Modular Expansion Joints, Phase 3

While expansion joints are a necessary component of bridges, they also contribute to noise pollution. Previous studies have investigated the design and feasibility of strategies to mitigate noise caused by modular expansion joints on bridges in Washington state. This study is Phase 3 of an effort to develop a highly durable sound attenuation system in which researchers will perform laboratory-based testing of noise mitigation prototypes. The prototypes will be injected with mixtures of fiber-reinforced, natural, and synthetic rubber with protective additives. The researchers will use a selection of low-density foam to fill gaps for increased durability and protection against roadway debris. Finally, they will use laboratory equipment to evaluate the prototype systems for hydraulic compression, cyclic fatigue, weathering of the system, adhesive durability, abrasion between the prototype and the seal, and susceptibility to debris.

Principal Investigator: Per Reinhall, Mechanical Engineering, UW
Sponsor: WSDOT
WSDOT Technical Monitor: Omar Jepperson
WSDOT Project Manager: Mustafa Mohamedali
Scheduled completion: November 2026

Development of a Specification for Quality Acceptance of Chip Seals Using a Laser Texture Scanner

Chip seals are widely used in Washington state as a cost-effective pavement surfacing method. However, they can be subject to variations in performance and premature failures. This project developed a quality acceptance specification for chip seal construction that incorporates the use of a laser texture scanner to provide valuable, data-driven insights for quality control and performance assessment to enhance the quality and effectiveness of chip seals.

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Washington State Rest Area Site Evaluation Study

Washington state has 42 safety rest areas. These rest areas differ in their capacity, facilities, and accessibility in each traffic direction. Some are located at the most traffic-dense corridors such as I-5 and I-90, whereas others are on less traffic-dense state routes. This project provided information on Washington rest area use and user experiences and evaluated the impacts of rest areas on traffic safety.

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