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  rehabilitationor 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 bridgeYear builtVessel clearanceOwned 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

48 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

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.