US Bridges

State Route 1 NB over Southgate Avenue

Fair

San Mateo County, California · 04-SM-001-R47.62-DLC · Structure no. 35 0238R

Built
1968
57 years old
Condition
Fair
inspected October 2024
Type
Box Beam or Girders - Multiple
Concrete Continuous
Length
168 ft
3 main spans
Daily traffic
32,500
2009 count
Owner
State
State Highway Agency

About this bridge

State Route 1 NB over Southgate Avenue is a concrete continuous box beam or girders - multiple carrying State Route 1 NB over Southgate Avenue in San Mateo County, California. It was built in 1968, so it is 57 years old, older 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 32,500 vehicles a day, roughly 2% of them trucks, projected to reach 48,210 by 2042. The structure is 168 ft (51.2 m) long and 51 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesState Route 1 NB
CrossesSouthgate Avenue
Location04-SM-001-R47.62-DLC
RouteState Highway 1
CountySan Mateo County
StateCalifornia
Coordinates37.67566, -122.47266
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionOctober 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating53.6 US tons
Inventory rating41.4 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialConcrete Continuous
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length168 ft (51.2 m)
Longest span81 ft (24.7 m)
Deck width51 ft (15.5 m)
Roadway width49 ft (14.9 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic32,500 (2009)
Projected traffic48,210 by 2042
Trucks2%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was State Route 1 NB over Southgate Avenue built?

It was built in 1968, making it 57 years old in 2025.

What condition is State Route 1 NB over Southgate Avenue 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 October 2024.

How much traffic does State Route 1 NB over Southgate Avenue carry?

About 32,500 vehicles per day (2009 count), of which roughly 2% are trucks.

How long is State Route 1 NB over Southgate Avenue?

The structure is 168 ft (51.2 m) long with a longest span of 81 ft (24.7 m) and a deck 51 ft wide.

Who owns State Route 1 NB over Southgate Avenue?

It is owned by the State Highway Agency.