Inspecting our bridges & structures

WSDOT inspects the approximately 7,300 bridges on state, city and county road systems. Most are inspected every two years. 

Inspecting the superstructure of the Lewis  and Clark Bridge, 340 feet above the  Columbia River.

We inspect bridges

  • To make sure they are in good working order.
  • To help prioritize our maintenance and preservation work.



  • In Fiscal Year 2015, WSDOT performed 2,106 bridge inspections, including 238 inspections that used an under-bridge-inspection-truck (UBIT) to allow inspectors to access every part of the bridge.
  • WSDOT’s Bridge office has 44 trained engineers and technicians to perform bridge inspections. These include specialized teams like the dive team that performs work under water and the mechanical and electrical inspectors that inspect moveable parts of a bridge.
  • WSDOT is nationally known for its high level of structural technical expertise.
  • The number of Bridge Inspectors has grown since 1998 to match the increasing inventory of state owned bridges.
  • Local agencies, which follow the same federal guidance for inspections, performed 2,412 bridge inspections in Fiscal Year 2015. Even though most local governments inspect their own bridges, WSDOT conducts field reviews and provides training and technical assistance to Washington cities and counties for inspecting bridges on local roads.

Photo of WSDOT crews inspecting the Alaskan Way Viaduct.

Inspection Schedules


WSDOT’s Bridge Preservation office is responsible for keeping bridge inspections on schedule; however logistical challenges can make it difficult. Challenges include:

  • Reduced work windows because of high traffic demands thus limiting inspectors’ access to key sections of bridges.
  • More stringent regulatory obligations also require adjustments to inspection schedules to accommodate nesting periods of protected migratory bird species.
  • Inspection schedules have flexibility built to accommodate unplanned inspections in the case of a bridge suffering unexpected damage.
  • New FHWA inspection performance measures require a bridge to be inspected as close as possible to the date plus the inspection cycle (typically 2 years).

Challenges in bridge inspections

  • Limited access to key sections of bridges due to high traffic demands.
  • Stringent regulations protecting migratory birds and nesting periods limits when inspections can take place.
  • Emergency bridge inspections may pull inspectors away from regular schedule.

State-owned bridge inspection ratings:

  • Good/Very Good - A range from no problems to some minor deterioration of structural elements. 
  • Fair - All primary structural elements are sound but may have deficiencies such as minor section loss, deterioration, cracking, spalling or scour. This is the most cost-effect time to rehabilitate before the underlying structure is damaged.
  • Poor - Bridges classified in "Poor" condition are monitored, repaired or replaced. These bridges are prioritized for future work as part of WSDOT's Bridge Preservation Program. A "Poor" rating is the Federal Highway Administration’s new rating term for bridges previously described as "structurally deficient."
    A bridge in "Poor" condition does not mean the bridge is unsafe for travelers or in danger of collapse. Bridge inspectors have authority to close or restrict any bridge deemed unsafe at any point during an inspection.
    The actual number of bridges in "Poor" condition varies as work is completed and bridges are inspected. Depending on inspection schedule timing, a bridge with completed work may remain on the list until the next inspection is completed.