US Bridges

NB State RTE 280 over Serramonte Boulevard

Poor

San Mateo County, California · 04-SM-280-R24.63-DLC · Structure no. 35 0209R

Built
1967
58 years old
Condition
Poor
inspected February 2025
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
129 ft
2 main spans
Daily traffic
89,000
2009 count
Owner
State
State Highway Agency

About this bridge

NB State RTE 280 over Serramonte Boulevard is a concrete continuous box beam or girders - multiple carrying NB State RTE 280 over Serramonte Boulevard in San Mateo County, California. It was built in 1967, so it is 58 years old, older than the California average of 54.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 89,000 vehicles a day, roughly 1% of them trucks, projected to reach 130,062 by 2045. The structure is 129 ft (39.3 m) long and 70 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

Location

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CarriesNB State RTE 280
CrossesSerramonte Boulevard
Location04-SM-280-R24.63-DLC
RouteInterstate 280
CountySan Mateo County
StateCalifornia
Coordinates37.66971, -122.46579
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck4 PoorAdvanced section loss, deterioration, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionFebruary 2025
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating60.4 US tons
Inventory rating36 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length129 ft (39.3 m)
Longest span70 ft (21.3 m)
Deck width70 ft (21.2 m)
Roadway width66 ft (20.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic89,000 (2009)
Projected traffic130,062 by 2045
Trucks1%
Lanes on structure4
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed3.1 mi (5 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$1.4 million (2020 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was NB State RTE 280 over Serramonte Boulevard built?

It was built in 1967, making it 58 years old in 2025.

What condition is NB State RTE 280 over Serramonte Boulevard in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in February 2025.

How much traffic does NB State RTE 280 over Serramonte Boulevard carry?

About 89,000 vehicles per day (2009 count), of which roughly 1% are trucks.

How long is NB State RTE 280 over Serramonte Boulevard?

The structure is 129 ft (39.3 m) long with a longest span of 70 ft (21.3 m) and a deck 70 ft wide.

Who owns NB State RTE 280 over Serramonte Boulevard?

It is owned by the State Highway Agency.