SDOT made an interim update to our dynamic Low Bridge Access Policy to expand access to select users.

With support from Mayor Durkan’s office and the West Seattle Bridge Community Task Force, we initiated an interim update to our dynamic Low Bridge Access Policy to increase access to the Lower Spokane Street Swing Bridge (Low Bridge) before automated enforcement is installed and put into effect in Fall 2020. Limited access is granted to specific employer shuttles, Metro vanpools for essential healthcare workers, and proximate maritime employees using the Low Bridge for work purposes only. 

Public safety is our top priority and the reason why we restricted use of the Low Bridge to emergency response vehicles, freight, and transit as soon as the High-Rise Bridge closed on March 23.  The Low Bridge has also been asked to play an outsized role in our transportation network, which is why we are rapidly moving forward with a body of work to ensure the Low Bridge can continue to serve these critical needs.  

Since March, many users and businesses have requested access to the Low Bridge. We have heard these requests and have actively been trying to find equitable ways to open the bridge to more users, without impacting public safety. 

After close monitoring of the Low Bridge and nearby streets, we determined that the Low Bridge can handle about 450 vehicles in either direction each hour before significant backup occurs, gridlocking drivers and shutting out crucial emergency access (read all about the data behind this number in a previous blog).  

Looking at hourly traffic counts while the Low Bridge was limited to emergency vehicles, freight, and transit, we determined there was space for about 160 more vehicles an hour in either direction during the day, before reaching that 450 vehicle cap mentioned above.  

At night, however, traffic volumes were lower, and it seemed advisable to open the bridge to all vehicles from 9 pm to 5 am.  

On June 25, we brought this information and a handful of proposals to the West Seattle Bridge Community Task Force and asked for their feedback on how to equitably allow more use of the Low Bridge.  

The Community Task Force recommended opening up the Low Bridge to all users overnight from 9 pm to 5 am and expanding daytime access to school buses and shuttles, which we implemented immediately. They also recommended that we gather further data to consider expansion for other critical or proximate uses.

Over the past month, we continued collecting data to see how hourly traffic volumes changed after adjusting the access policy, and we worked with businesses and stakeholder groups to develop a plan to allocate the very limited 160 slots in an equitable way.


At the Community Task Force meeting on July 22, 2020, we presented our updated policy that grants limited access for specific employer shuttles, Metro vanpools for essential healthcare workers, and proximate maritime employees using the Low Bridge for work purposes only.  

This is a dynamic access policy that we will continue to monitor and adjust where needed, and will be adapted in the fall when new automated camera enforcement will be installed.

Though the Community Task Force was pleased with the changes to the policy, they brought up compelling questions that many community members are also wondering.  


Why does the overnight open access begin at 9 pm? Is it possible to open it earlier such as at 8 pm?  

The decision to open the bridge at 9 pm was based off hourly traffic counts that showed a significant drop in us between the 8 pm and 9 pm hours.  

Currently, both directions of the Low Bridge have traffic volumes that are not only up, but higher than 400 vehicles per hour between 9 and 10 pm, nearing the 450 vehicles in either direction threshold that would impede emergency access.  

Based on this data, if we were to allow access prior to 9 pm, even just one hour earlier at 8 pm, we anticipate that use of the Low Bridge would exceed that critical 450 vehicles threshold. With safety as our number one priority, we cannot take that risk.  


Can the Low Bridge be opened to all vehicles during weekend days?  

Not at this time. Our hourly traffic counts show that weekend traffic has increased and that there are already a few hours in the evening where levels surpass the 450 vehicle per hour threshold, and many hours where traffic levels are approaching the threshold.  

Without a scalable enforcement mechanism in place, we are not currently able to expand general public use of the Low Bridge during all weekend hours, only the same 9pm to 5am general use window.  


Can motorcycles use the Low Bridge?  

No, motorcycles are not currently allowed under the dynamic Low Bridge Access policy.  

While an individual motorcycle is clearly smaller than a car, they still require roughly the same amount of room on all sides to travel safely. This is because a large truck or bus needs just as much room to stop safely when they are following a motorcycle as they do for any other kind of vehicle. While two motorcycles could theoretically travel side by side, most motorcycles would likely be travelling on their own and occupy an entire lane.  

This means that from a traffic engineering perspective, motorcycles take up essentially the same amount of room as a car. This is especially true in stop-and-go conditions where congestion is created by the cumulative reaction time of every individual driver waiting to go forward after the vehicle in front of them moves ahead. In other words the number of vehicles in a line of traffic is just as important as the size of each individual vehicle, and so motorcycles could be expected to add to congestion at the Chelan 5-way intersection just like cars do. 

We also have safety concerns about motorcycles travelling next to large trucks and buses in stop-and-go conditions, especially because congestion would likely increase considerably if more motorcycles took this route. 

We are grateful to have Community Task Force members raise the concerns of their communities and ask these questions.

If you missed the Community Task Force meeting this week, you can watch a recording of the meeting below. The next meeting will be held on August 5. We will share a link to watch the meeting live closer to that date. Be sure to sign up for West Seattle Bridge emails to receive the Community Task Force meeting invites and other important bridge announcements.  

If you haven’t yet, fill our your Reconnect West Seattle survey and Neighborhood Prioritization Ballots by next Friday, July 31.  If you have questions or need assistance, please drop into one of our Reconnect West Seattle office hours next week.   


Reconnect West Seattle Virtual Office Hours  

Next week, stop by SDOT’s virtual office hours to get your questions answered about the Reconnect West Seattle and the neighborhood prioritization process. Technical experts will be available to provide more details and answer questions before the ballots and surveys close on July 31. 

  • Session one is Wednesday, July 29 from 12 PM – 1 PM 
    • Link to the online meeting. 
    • Audio conference information: To receive a call back, provide your phone number when you join the event, or call the number below and enter the access code.  
      • +1-408-418-9388  
      • Event number (access code): 146 470 3249 

  • Session two is Thursday, July 30 from 6:30 PM – 7:30 PM 
    • Link to the online meeting. 
    • Audio conference information: To receive a call back, provide your phone number when you join the event, or call the number below and enter the access code.  
      • +1-408-418-9388  
      • Event number (access code): 146 492 4055