US Bridges

State Route 84 over San Francisco Bay-South

Fair

San Mateo County, California · 04-SM-084-R29.25-MLP · Structure no. 35 0038

Built
1981
44 years old
Condition
Fair
inspected June 2023
Type
Box Beam or Girders - Multiple
Steel Continuous
Length
8,600 ft
15 main spans
Daily traffic
62,000
2021 count
Owner
State
State Highway Agency

About this bridge

State Route 84 over San Francisco Bay-South is a steel continuous box beam or girders - multiple carrying State Route 84 over San Francisco Bay-South in San Mateo County, California. It was built in 1981, so it is 44 years old, younger than the California average of 54.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 62,000 vehicles a day, roughly 4% of them trucks, projected to reach 90,000 by 2045. The structure is 8,600 ft (2,621.3 m) long and 85 ft wide. If it were closed, the detour would be 26.7 mi (43 km).

Location

Open in Google Maps
CarriesState Route 84
CrossesSan Francisco Bay-South
Location04-SM-084-R29.25-MLP
RouteState Highway 84
CountySan Mateo County
StateCalifornia
Coordinates37.49915, -122.12838
Functional classUrban Principal Arterial - Other Freeway or Expressway

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJune 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour within limits of footing or piles
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating42.1 US tons
Inventory rating31.1 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans15 (+70 approach)
Design loadHS 20
Structure length8,600 ft (2,621.3 m)
Longest span340 ft (103.6 m)
Deck width85 ft (25.9 m)
Roadway width70 ft (21.3 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic62,000 (2021)
Projected traffic90,000 by 2045
Trucks4%
Lanes on structure6
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesOther
Detour if closed26.7 mi (43 km)
TollToll bridge
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusEligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNavigation control on waterway (bridge permit required)

Frequently asked questions

When was State Route 84 over San Francisco Bay-South built?

It was built in 1981, making it 44 years old in 2025.

What condition is State Route 84 over San Francisco Bay-South in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in June 2023.

How much traffic does State Route 84 over San Francisco Bay-South carry?

About 62,000 vehicles per day (2021 count), of which roughly 4% are trucks.

How long is State Route 84 over San Francisco Bay-South?

The structure is 8,600 ft (2,621.3 m) long with a longest span of 340 ft (103.6 m) and a deck 85 ft wide.

Who owns State Route 84 over San Francisco Bay-South?

It is owned by the State Highway Agency.