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Bridge conditions in San Mateo County, California

361 inventoried bridges · 37 rated poor · 2025 National Bridge Inventory

United States Bridge Conditions2025 National Bridge Inventory, FHWACompiled August 20, 2026

Of the 361 San Mateo County bridges in the federal inventory, 37 carry a poor rating. That 10.2% share is roughly 2x the national average.

37 of the 361 bridges in San Mateo County, California, are rated in poor condition (10.2%) in the 2025 National Bridge Inventory, as of August 20, 2026.
100 bridges (27.7%) are rated good and 224 (62.0%) fair.
The median San Mateo County bridge was built in 1969.
The busiest poor-rated bridge is U.S. Highway 101 over Cordilleras Creek (built 1930), carrying about 195,000 vehicles a day.

Good 27.7% · Fair 62.0% · Poor 10.2% of 361 bridges

Bridges rated poor

Every bridge in the county with a poor rating, busiest first. Poor means a major component is rated 4 or lower on FHWA's 0-9 scale; it is a repair flag, not a closure notice.

Bridge	Built	Vehicles/day	Condition
U.S. Highway 101 over Cordilleras Creek	1930	195,000	Poor
Interstate 280 over Southgate Avenue	1967	178,000	Poor
State Route 92 over San Francisco Bay	1967	120,000	Poor
US Highway 101 SB over Caltrain UP RR Grand Onr	1948	98,000	Poor
US Highway 101 NB over Caltrain UP RR Grand Onr	1948	98,000	Poor
SB State Rte 280 over Serramonte Boulevard	1967	89,000	Poor
NB State Rte 280 over Serramonte Boulevard	1967	89,000	Poor
Interstate 280 SB over Avalon Drive	1971	50,500	Poor
Interstate 280 NB over Avalon Drive	1971	50,500	Poor
Interstate 280 over Farm Hill Boulevard	1969	50,000	Poor
I-280 Northbound over Alpine Rd & Los Trancos	1969	46,500	Poor
Interstate 280 SB over San Francisquito Creek	1969	46,500	Poor
Interstate 280 NB over San Francisquito Creek	1969	46,500	Poor
Hillsdale Blvd over Marina Lagoon	1963	46,460	Poor
Interstate 280 NB over Farm Hill Boulevard	1969	44,500	Poor
N101-w380 Connectr over I 380 US 101 7TH Conn	1976	43,500	Poor
State Route 84 over Caltrain UP RR Shasta St	1965	43,000	Poor
E380-s101 Connectr over S101-san Bruno Av 7TH Av	1976	42,000	Poor
Departing Flt Trfc over Arriving Flight Traffic	1973	19,170	Poor
Spruce Ave over Colma Creek	1975	17,332	Poor
N101-bayshore Off over US Highway 101	1957	8,000	Poor
Linden Ave over Colma Canal	1974	7,160	Poor
Airport Blvd over Burlingame Lagoon	1970	7,000	Poor
W380-n&s101 Conn over US 101 I 380 EB Con Rmps	1976	5,000	Poor
Bridge Dr Parkway over Redwood Shores Lagoon	1971	2,600	Poor
Main St over Pilarcitos Creek	1900	2,350	Poor
Bradford St over Redwood Creek	1966	2,000	Poor
Bermuda Dr over Fiesta Channel	1955	1,920	Poor
Tartan Trail Rd over San Mateo Creek	1964	1,887	Poor
North Access Rd over San Bruno Channel (E)	1986	1,000	Poor
Bridge Dr Parkway over Redwood Shores Lagoon	1971	1,000	Poor
Gazos Creek Road over Gazos Creek	1982	218	Poor
El Prado Road over Easton Creek	1956	200	Poor
Wurr Rd over Pescadero Creek	1962	91	Poor
Main Road over Little Butano Creek	1980	70	Poor
Pilarcitos Creek R over Pilarcitos Creek	1910	42	Poor
State Park Rd over Little Butano Creek	1983	25	Poor

Busiest bridges in the county

Bridge	Built	Vehicles/day	Condition
U.S. Highway 101 over San Mateo Creek	1928	236,000	Good
US 101 Rollins Rd over Transmission Canal	1928	232,000	Fair
US 101 Mcdonnell over Millbrae Slough	1947	226,000	Fair
US 101 W&e Bayshr over San Francisquito Creek	2018	225,800	Good
Holly Street over US Highway 101	1954	201,000	Fair
Whipple Avenue over US Highway 101	1958	201,000	Good
U.S. Highway 101 over Marsh Creek	1930	199,000	Fair
U.S. Highway 101 over SR 84 (woodside Road)	1958	199,000	Good
U.S. Highway 101 over Caltrain UP RR Sierra Pt	1956	196,000	Fair
U.S. Highway 101 over Oyster Point Drain	1995	196,000	Good

Source: FHWA National Bridge Inventory, 2025. Counts cover inventoried highway bridges over 20 feet; ratings are reported by the state DOT.

All of California: California bridge conditions by county · every download on the data page.

Background: how bridge ratings work · what "poor" and "structurally deficient" actually mean · how often bridges are inspected.