Sonoma County Bridge Report Card

Sonoma County scores 74 out of 100 on BridgeLookup's Bridge Condition Exposure Score, based on FHWA National Bridge Inventory records.

C74 / 100

Local infrastructure snapshot

Sonoma County, California

Sonoma County has 611 bridges in the National Bridge Inventory, with 32 rated poor and 25 rated scour-critical. Its poor-condition share of 5.2% is above the 4.9% statewide average. Poor-condition bridges carry about 252,564 daily vehicle crossings.

611Total Bridges

32Poor (5.2%)

441Fair (72.2%)

25Scour-Critical

Quote-Ready Local Facts

5.2%of county bridges are in poor condition, compared with 4.9% statewide and 6.7% nationally.

252,564daily vehicle crossings are on poor-condition bridges in the county.

25bridges are rated scour-critical, or 4.1% of the county bridge inventory.

Copyable Facts for Reporters

BridgeLookup.com gives Sonoma County a Bridge Condition Exposure Score of 74/100 (C). The county has 611 bridges in the National Bridge Inventory, including 32 in poor condition and 25 rated scour-critical. Poor-condition bridges carry about 252,564 daily vehicle crossings. Poor condition does not mean unsafe; bridges judged unsafe are closed or restricted by transportation agencies.

Download all county report-card scores as CSV.

How the Score Breaks Down

Factor	Weight	County Value	Penalty
Poor-condition bridge share	40	5.2%	10.5
Poor-condition traffic exposure	25	3.9% of measured traffic	2.9
Scour-critical bridge share	20	4.1%	8.2
Average age vs national baseline	10	58 years vs 48 nationally	4.0
Traffic-data completeness	5	6,427,509 measured daily crossings	0.0

Score = 100 minus weighted penalties. The score is a comparative research signal, not an official safety rating. Read the full methodology.

County Comparisons

County Poor-Condition Share	5.2%
State Poor-Condition Share	4.9%
National Poor-Condition Share	6.7%
County Scour-Critical Share	4.1%
Average Bridge Age	58 years
Poor-Condition Traffic Exposure	252,564 vehicles/day

Bridges to Watch

Busiest Poor-Condition BridgeUS Highway 101 over Dry Creek Road — 45,500 vehicles/day Oldest Listed BridgeState Route 128 over Header Draw — built in 1900 All County BridgesBrowse every bridge record in Sonoma County.

Top Bridges to Watch in Sonoma County

Bridge	Reason	Condition	Daily Traffic	Year Built
River RD over Mark West Creek	Poor condition + traffic exposure	Poor	8,000	1958
Franz Valey Sch RD over Franz Creek	Poor condition + traffic exposure	Poor	350	1946
Mill Creek RD over Mill Creek	Poor condition + traffic exposure	Poor	210	1961
Sweetwtr Sprngs RD over Porter Creek	Poor condition + traffic exposure	Poor	140	1968
US Highway 101 over Dry Creek Road	Poor condition + traffic exposure	Poor	45,500	1960
U.s. Highway 101 over Westside RD	Poor condition + traffic exposure	Poor	45,500	1960
US Highway 101 SB over Chiquita Road	Poor condition + traffic exposure	Poor	22,500	1960
Washington ST over Petaluma River	Poor condition + traffic exposure	Poor	21,900	1970
Old Redwood HWY over Willow Brook Creek	Poor condition + traffic exposure	Poor	19,980	1999
Arnold DR over Sonoma Creek	Poor condition + traffic exposure	Poor	13,900	1924

Important safety note

Poor condition does not mean a bridge is unsafe. It means at least one major component has significant deterioration and the bridge is a priority for maintenance, repair, or replacement. Bridges judged unsafe are closed or restricted by transportation agencies.