Seattle’s first fully-protected intersection is now open at Dexter/Thomas
The goal: No more deaths or serious injuries at Dexter and Thomas.
This seemingly unremarkable intersection has been the site of at least two tragedies in recent memory. Mike Wang was killed by someone making a left turn there while biking home from work in 2011, and Jaahnavi Kandula was killed by a speeding Seattle Police officer while walking in the crosswalk in 2023. Though this project was planned before Kandula was killed, its opening this week feels like the city is saying, No more. Not again. Not here."
The new design includes several features Seattle has not used previously, but they are all designed to maximize safety by slowing motor vehicles, shortening crossings, separating modes of travel, and creating redundant safety buffers. It is something of a showcase of safety features, a test of what a high-budget, complete rebuild intersection project could look like. There are curbs and separators all over the place, carefully placed to slow turning traffic, improve sight lines between all users, and make it clear where everyone is supposed to be.
Aerial photo from SDOT.I observed the new protected intersection at Dexter and Thomas for a while Monday, and it seemed like most people had no problems figuring out what to do. The biggest issue I observed was that some drivers wanted to turn left, which is no longer allowed. One person drove in the bike lane to do it, and another sat there confused for a while before finally deciding to turn right.
But even the person who drove in the bike lane to turn left didn't create a super dangerous situation because they were moving so slow when doing it. Obviously it was not ideal, but that's the big takeaway I had from riding through it from every direction and observing others use it: There are redundant safety features. For example, let's say someone in a car wants to turn right. First, they have to take a sharp, slow turn so they are already moving relatively slowly. Then there is a long maybe ten-foot buffer area where their car is turning but they have not yet entered the path of the bike lane. This buffer area accomplishes two important things: 1) The person driving has a lot of extra time to see people in the bike lane and crosswalk and yield to them. 2) The people biking and using the crosswalk have a lot of extra time to see that someone is turning and to look out for them. So even if the driver completely fails in their duty to yield, everyone else has a lot more time to avoid a collision. That's what I mean by redundant safety features. Several things need to all go wrong in a row before someone is hurt or killed.
Redundancy is a vital feature of any safe system, whether we are talking about a factory or an airplane or a public street. People make mistakes, so we need to design systems in a way that accounts for those mistakes. While the U.S. has embraced a safe systems approach to workplace safety (thanks in large part to labor unions) and air travel (insert Boeing joke here), our public roadways are almost entirely designed so that even a small mistake by a single person can end in tragedy. At most intersections, it only takes a moment of inattention for a person turning right to strike someone in a crosswalk or right hook someone on a bike. Maybe the person was hidden for a moment by the pillar next to the car windshield or maybe the driver was looking to the left for a break in traffic and started moving before checking to the right. There is no backup safety process to prevent a tragedy.
People biking probably have the biggest learning curve here, especially if they want to turn left. Doing so now requires making a two-step turn by crossing straight with the green bike light, then turning and stopping in the waiting area on the far side until the signal changes again. It's easy to figure out, but it does require waiting potentially for two full signal cycles to get through. That's the trade-off for all the extra separation. People who don't want to wait and who feel comfortable biking in traffic can always turn a block before or after using the left turn lane, but now there's a complete solution for people who don't feel comfortable merging across traffic or who are willing to wait in exchange for increased safety and comfort.
There is still a lot of work to do on Thomas Street, but it is now mostly ready to play the role of the best biking and walking connection between South Lake Union and Seattle Center. I'm remembering back a decade to before the Mercer Street bikeway under Aurora opened when it was next to impossible to bike between these places. What a difference.
It would be very pricey and take a very long time to turn every intersection in Seattle into what Dexter and Thomas is now. It would be amazing if this style of intersection becomes part of the standard street rebuild process for high-budget projects. I am also hopeful that by learning from this design, SDOT can take the most important elements and apply them to lower-budget projects that can be built much faster across the city. Because while this one intersection had seen far more than its share of tragedy and heartbreak, it's just one of thousands.
If you want to see the intersection in action, check out today's video from Best Side Cycling: