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Key Takeaways:
- The most crash-prone intersection in Washington is SR 204 & SR 9 in Lake Stevens, with 272 crashes over a four-year period. This location also recorded the highest number of minor injuries, with 36 reported incidents.
- Four of the top six most crash-prone intersections are roundabouts.
- Among the top 30 most crash-prone intersections, five are in Kent—more than any other city.
- At the county level, King County stands out with 10 of the 30 most crash-prone intersections.
- The intersection of Hwy 99/Evergreen Way and Airport Rd. experienced the highest severity crashes, reporting three fatalities and five serious injuries within a four-year period.
- Seattle leads in intersection crashes between 2021 and 2024, with 14,410 incidents, followed by Tacoma (11,264) and Spokane (10,999).
Washington has experienced steady population growth in recent years, driven by a strong job market, vast green spaces for outdoor recreation, and its own major city, Seattle. This growth has led to increased traffic volumes, with more commuters, tourists, and new residents navigating the state’s roads.
As cities expand and suburban areas develop, road design and infrastructure are increasingly scrutinized for safety. Among the many factors considered, intersections stand out as critical points where traffic flow, visibility, and signal timing can significantly impact driver safety. Intersections are among the most common locations for crashes. Some fail to meet ideal safety conditions, while others have undergone updates in response to persistent crash trends.
For this study, we analyzed Washington State Patrol collision data from 2021 to 2024 to identify the 30 most crash-prone intersections in the state.
Our analysis includes a detailed look at the intersection with the highest number of crashes, where a recent conversion to a roundabout led to an unexpected rise in collisions. We also examine crash severity proportions, the distribution of crashes by city, and a mapped overview of the most dangerous intersections in the state.
Where Intersection Crashes Happen Most in Washington
The following list highlights the 30 most crash-prone intersections in Washington from 2021 to 2024, based on the number of reported collisions at each location.
The most crash-prone intersection in Washington is the SR 204 and SR 9 roundabout in Lake Stevens, with a significant 272 crashes, far exceeding any other location. Interestingly, four of the top six intersections feature roundabouts. Roundabouts are designed to replace traditional intersections, improve traffic flow, and reduce the severity of crashes, such as fatal and injury collisions. This reduction in risk is achieved by lowering speeds and eliminating high-risk “T-bone” and head-on collisions. However, the roundabout design may also contribute to frequent minor collisions. As roundabouts have only been implemented in Washington state over the past 30 years, the unfamiliarity with this road design can lead to driver confusion, especially when one roundabout feeds into another, as seen at the SR 204 & SR 9 roundabout.
Many other of the high-crash intersections are located on major highways and roads, such as SR 18, SR 526, I-5, and SR 395. These locations are often heavily trafficked, which increases the likelihood of crashes, particularly where high-speed roadways intersect with urban areas or complex interchanges.
Moreover, certain cities appear multiple times on the list, indicating hotspots for crashes. Kent has five high-crash intersections, highlighting its role as a traffic-heavy area. Federal Way and Everett each have three. Kennewick, Lakewood, and Tacoma also appear multiple times, suggesting ongoing crash issues in these urban centers. At the county level, King County stands out with 10 of the 30 most crash-prone intersections. Positioned between Seattle and Tacoma, King County serves as a major corridor for commuters traveling between these cities. Many residents live in Kent but work in nearby urban centers. Snohomish County follows with six, while Benton County has three, showing that although the most frequent crashes occur in the Seattle metro area, collisions are widespread in growing regions.
A Closer Look at the Most Crash-Prone Intersection in Washington
The SR 204 & SR 9 roundabout in Lake Stevens stands out not just for its high crash numbers but also for the way it reflects a community adapting to a roadway change that still feels unfamiliar to many drivers. Below is a detailed list of crashes over a four-year period, offering insight into this transition.
The SR 204 and SR 9 intersection was recently converted into a roundabout as part of a $69 million project completed in the summer of 2024. The project introduced four new roundabouts and an additional lane on SR 9 near Frontier Village to improve traffic flow for commuters, freight vehicles, and businesses. While safety was also a key consideration—studies show that roundabouts can reduce injury crashes by 72% to 80% and lower overall crash rates by 35% to 47%—the transition has presented challenges.
Crash data reveals a sharp increase in reported collisions at this intersection. Between 2021 and 2024, crashes rose from 14 in 2021 to 150 in 2024. However, not all of these crashes occurred after the roundabout was completed, and only one serious injury crash was recorded during this four-year period, which happened before the conversion. Meanwhile, the adjacent roundabout of SR 9 and Vernon Road, 0.2 miles away, recorded 57 collisions in the same time period, with 39 occurring in 2024.
Because roundabouts are still a relatively new addition to Washington’s roadways, WSDOT took proactive steps to help drivers adjust. Before and after the new roundabouts opened, the agency set up three informational pop-ups in Lake Stevens. These events gave residents the opportunity to learn how to navigate the new design, ask questions, and voice any concerns about the changes. Despite these efforts, local reactions remain mixed, with some drivers voicing frustrations.
One Reddit user noted, “The only issue with the roundabouts here is speed. People are trying to go 35-45 [mph] through these instead of 15-20 [mph]. I’d really like to see WSDOT figure out a way to slow people down at these roundabouts.”
Others have raised concerns about narrow lanes that make it difficult for logging trucks to navigate, poor signage visibility, and confusion caused by the multi-roundabout system, which was mentioned in the most upvoted comment on the thread.
How Long Does It Take Drivers to Adjust to Roundabouts?
Research shows that an increase in driver errors is common when a new traffic feature is introduced, especially at multi-lane roundabouts. A 2007 Federal Highway Administration study in Oregon found that mistakes at an urban two-lane roundabout followed a “learning curve” pattern, stabilizing around six months after installation. Similarly, a 2017 study in Fredericton, New Brunswick, observed a surge in errors after the introduction of a double-lane roundabout. The most frequent mistake was drivers changing lanes within the roundabout, while the most crash-prone error was failing to yield to circulating traffic. Most errors began to decline within 15 to 20 weeks, with total errors leveling off at around 24 weeks. After a year, total mistakes had decreased by 74%.
Analyzing Crash Severity for the Top Intersections
We know that the most crash-prone intersection has largely seen minor collisions, but how does it compare to the others on the list? Here, we break down the severity of crashes at each of the top 30 intersections.
Several intersections on this list have no recorded fatal crashes, with only 23% experiencing at least one fatality. The intersection of Hwy 99/Evergreen Way and Airport Rd. reported the most fatalities, with three over a four-year period, accounting for 4% of its crashes. This location also has the highest count and proportion of serious injuries, with five incidents making up 6% of its total crashes. For minor injuries, the SR 204 & SR 9 roundabout has the highest count, with 36 reported cases. However, the intersection at S 19th St. and S Sprague Ave. stands out for its proportion of minor injuries, reporting 30 incidents, representing 37% of its crashes.
Intersection Crash Distributions by City
In addition to our intersection-level analysis, we also examined crash counts by city across Washington. The chart below provides a comparison of intersection crash totals by city, offering a broader perspective on regional traffic safety challenges. The table reveals that major metropolitan areas account for the majority of intersection crashes in Washington. Seattle leads the list with 14,410 incidents, followed closely by Tacoma (11,264) and Spokane (10,999), which is not surprising given their high traffic volumes and dense populations. Suburban hubs like Kent, Vancouver, and Everett also report significant numbers, with counts of 5,991, 5,854, and 4,694 respectively. In contrast, smaller cities such as Poulsbo, Oak Harbor, and others register lower crash totals, yet their figures remain notable.
Addressing Intersection Safety in Washington
Our analysis of intersection crash data in Washington from 2021 to 2024 reveals distinct patterns and challenges in the state’s transportation network. While the SR 204 & SR 9 roundabout in Lake Stevens demonstrates the potential for reduced crash severity, it also highlights the transitional challenges associated with new traffic designs, with early community pushback to be expected.
The data indicates that although roundabouts can lower the risk of fatal and serious injuries, driver unfamiliarity contributes to a temporary increase in minor collisions. However, research suggests that driving errors tend to decline and stabilize around 24 weeks. As the project was completed by the end of Summer 2024, analyzing upcoming data will help determine if the patterns align with these findings or if further adjustments, such as refining signage, modifying speed limits, or enhancing lane configurations, are needed.
To safely navigate roundabouts, drivers should slow down as they approach, yield to traffic already circulating, and enter when there is a safe gap. Once inside, maintaining a steady speed and avoiding lane changes can help reduce confusion for other drivers and minimize the risk of collisions. Lane discipline is a frequent issue, as drivers may enter the wrong lane for their intended exit and attempt last-minute lane changes. It is also essential to use turn signals when exiting to communicate intentions to other drivers. For pedestrians, using designated crosswalks and making eye contact with approaching drivers can enhance safety.
Discussions like this Reddit thread provide helpful explanations of how to navigate two-lane roundabouts, addressing common points of confusion such as lane selection and right-of-way.
While roundabouts are just one element of intersection safety, broader crash trends in Washington indicate that urban centers remain high-risk areas. Major urban centers such as Seattle, Tacoma, and Spokane account for the majority of intersection crashes, with suburban hubs like Kent and Everett also facing challenges. Notably, many of these high-crash cities are located in King County, which alone is associated with 10 of the 30 most crash-prone intersections. These patterns suggest that improving intersection safety requires not only better road design but also targeted interventions in high-risk areas. These findings suggest that continuous improvements in road design, enhanced signage, targeted enforcement, and ongoing public education are essential for reducing intersection crashes over time.
As drivers adapt to newer traffic management systems like roundabouts, it is crucial for policymakers and transportation planners to closely monitor these trends and implement further refinements to ensure safer roadways for all.
Methodology
We analyzed collision data from the Washington State Patrol (WSP) from 2021 to 2024 to identify the most crash-prone intersections. Using the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm, we grouped crashes occurring within 0.1 miles of each other to account for intersections with multiple entry and exit points. After running the clustering process, we manually verified the locations, cross-referencing them with street names in the dataset.
Fair Use Statement
You’re welcome to share our study with anyone who might find it useful. If you reference our findings in your own work, we kindly ask that you include a link to this page for proper attribution.