What we do

Some of Seattle's bridges make connections over bodies of water, like the West Seattle Bridge. Other bridges, like the Magnolia Bridge, are viaducts that make connections over valleys. Some bridges, like the Fremont Bridge, serve all travel modes and others are limited to foot or bike traffic, like the W Thomas St Overpass.

SDOT owns, inspects, maintains, and/or operates nearly 280 bridges. Bridge program work includes:

  • Bridge Painting Program: Painting steel and other metal on bridges protects them from corrosion and rust. The typical life of bridge paint is 18 years.
  • Bridge Load Rating Program: Managing the safe weight capacity of bridges is an important element to bridge safety. Activities include analysis of the weight capacity of bridges, field verification tests, and monitoring of instrumentation on deficient bridges.
  • Capital Improvement Program: Some bridges require major rehabilitation or replacement to ensure they remain safe and available to the traveling public. Capital projects often involve a multi-year planning, design, and engineering process.

This Capital Projects and Roadway Structures 2018 Annual Report provides information about SDOT's key structural assets: bridges, retaining wall, stairways and areaways.  Combined, these assets represent over $8.3 billion in replacement value. The report also highlights capital improvement projects that were completed or underway in 2018. 

Bridge openings

In the city, there are7 vehicular moveable bridges over navigable water, of which 4 are owned by SDOT. Federal law requires bridges open for marine traffic, with few exceptions. Seattle is part of the US Coast Guard 13th District. More information is available at

Seattle's moveable bridges

Here is a list of vehicular bridges in Seattle that open for marine traffic.

Moveable bridge Year built Vessel clearance Owned and operated by
Ballard bridge 1917 44 feet SDOT
Fremont Bridge 1917 30 feet SDOT
Montlake Bridge 1925 46 feet Washington State Department of Transportation
Spokane St Swing Bridge 1991 55 feet (at mean high tide) SDOT
South Park Bridge 2014 34 feet (at mean high tide) Owned by King County, Operated by SDOT
University Bridge 1919 42.5 feet SDOT
1st Ave S Bridge

1956, northbound

1996, southbound

39 feet (at mean high tide) Washington State Department of Transportation

Bridge opening schedule

Bridges open on request between 7 AM and 11 PM. From 11 PM to 7 AM, bridges open by appointment only. The average bridge opening, from the time street traffic stops to the time it resumes, lasts about 4 minutes. The Spokane St Swing Bridge openings last about 10 minutes.

Seattle's Ship Canal Bridges - University, Fremont, and Ballard Bridges - have restrictions in place during the morning and afternoon peak commute to help keep street traffic moving during busy hours. These 3 bridges stay closed to marine traffic on weekdays, from 7-9 AM and from 4-6 PM, except for federal holidays but Columbus Day and for any vessel of 1,000 gross tons or over. See the federal regulation for Lake Washington Ship Canal bridges here. Information on Montlake Bridge openings is available here.

How to request a bridge opening

· Between 7 AM and 11 PM, vessels should contact the bridge by radio (Marine Channel 13 or call (206) 386-4251) or use a whistle signal: one long, one short.

· The US Coast Guard requests pleasure vessel use a whistle signal from 7 AM to dusk.

· Between 11 PM and 7 AM, bridge openings are by appointment only, and should be requested no less than 1 hour prior to the opening.

· For openings by appointment, the bridge operator will wait 15 minutes after the appointment time before contacting the vessel on Marine Channel 13. If the bridge operator doesn't receive a response, the operator will leave for the next appointment. · For state- or county-owned bridges, visit or

Bridge Seismic Retrofit Program  

Safety for the traveling public is our number one priority. Every bridge is built to the earthquake standards of the time it is designed and receives ongoing maintenance. The bridge seismic retrofit program is one type of investment which goes above and beyond basic maintenance to bring sturdy but older bridges up to modern standards. The program is implemented in tandem with the basic bridge maintenance, regular inspections, monitoring, preservation, and repairs we perform continually to keep bridges safe.

We worked with industry subject matter experts to develop our Bridge Seismic Retrofit Program in 1990 and have since continued to work with experts to update and revise our Bridge Seismic Retrofit Philosophy, Policies, and Criteria. We are currently working on the latest revision of this document. In phase one of the program (1990-2005), we completed seismic retrofits on 23 bridges. In phase two (2006-2015 - thanks to the voter-approved Bridging the Gap Levy), we completed seismic retrofits on 7 bridges. 

We are currently in phase three of the program which is fully funded through the voter-approved Levy to Move Seattle.  

At the beginning of the Levy to Move Seattle, we estimated 16 new seismic retrofits could be completed based on the costs and level of effort to implement seismic improvements in phase one and two. It was always understood we would need to perform more complex modeling, inspection, and analysis to determine the specific improvements needed for each bridge listed in the Levy to Move Seattle. Similar to when one is preparing for home repairs, cost estimates often change when you take a deeper look and consider current codes. This happened when we did analysis for phase three of the Seismic Retrofit Program and higher costs were revealed. The change was because 1) estimates were based on older bridge projects which were completed first because they had simpler needs, and 2) engineering best practices have advanced in recent years and newer modeling assumptions help us to better understand how the soil around bridges would react to a large earthquake. The analysis led us to realize 5 of the bridges required much more complex investments to achieve current earthquake safety standards.

Knowing what we do now, we are focusing on the 11 bridges where analysis confirmed the investment makes sense. We are still committed to taking care of the other 5 bridges, and our plan is to conduct future evaluation to determine the best type of investment for each bridge (such as extensive seismic retrofits in a future phase of the program, or other kinds of rehabilitation or full replacement if that makes more sense). The planning going on now, sets us up for possible grant and new funding opportunities as they become available. 


Updated Status

Cowen Park Bridge 


W. Howe St Bridge 


SW Andover Pedestrian Bridge 


Admiral Way North Bridge 


Admiral Way South Bridge 


Delridge Pedestrian Bridge 


15th Ave NW/Leary Way Bridge 


15th Ave NE over 105th Ave NE 


McGraw St Bridge 


N 41st St Pedestrian Bridge 


8th Ave / 133rd Ave Bridge 


Ballard Bridge (Bascule) 

Future Evaluation 

Fremont Bridge (Bascule) 

Future Evaluation  

1st Ave over Argo RR Bridge 

Future Evaluation  

4th Ave over Argo RR Bridge 

Future Evaluation  

4th Ave S Bridge (Main St - Seattle Blvd) 

Future Evaluation  

Vehicle weight restrictions on bridges

Structure NameLocationWeight Restriction
Magnolia Bridge Center, Pier 91 ramps to Port of Seattle on Magnolia Bridge No trucks allowed
McGraw St Bridge McGraw Street over the ravine near 3rd Ave North AASHTO Type 3: 19 tons
AASHTO Type 3S2: 29 tons
Single truck, 4 axle: 17 tons
Single truck, 5 axle: 19 tons
Single truck, 6 axle: 18 tons
Single truck, 7 axle: 18 tons
E Interlaken Blvd East Interlaken Blvd over 26th Ave East 19 tons
Fairview Ave N (southbound) Fairview Ave N between East Galer and E Prospect streets 40 tons
Cowen Park Bridge 15th Ave NE between Cowen Place NE and NE 62nd St Single truck, 7 axle: 36 tons

For additional information about Commercial Vehicle Permits, contact Don Smith at (206) 684-5125.

For additional information on the SDOT Load Rating Program contact Yuling Teo at (206) 733-9244.


  • Protect the public's investment, extend the service life of bridges, and provide safe travel across bridges by all modes
  • Improve safety and reliability by rehabilitating bridges to meet structural standards
  • Maintain the historic character of Seattle's bridges
  • Practice innovative maintenance management to efficiently and cost effectively achieve these goals

Current projects

We are rehabilitating and replacing several bridges in the city. Visit the project webpages below to learn more.