Napa County Bridge Report Card
Napa County scores 70 out of 100 on BridgeLookup's Bridge Condition Exposure Score, based on FHWA National Bridge Inventory records.
Napa County, California
Napa County has 160 bridges in the National Bridge Inventory, with 8 rated poor and 6 rated scour-critical. Its poor-condition share of 5.0% is above the 4.9% statewide average. Poor-condition bridges carry about 103,912 daily vehicle crossings.
Quote-Ready Local Facts
Copyable Facts for Reporters
BridgeLookup.com gives Napa County a Bridge Condition Exposure Score of 70/100 (C). The county has 160 bridges in the National Bridge Inventory, including 8 in poor condition and 6 rated scour-critical. Poor-condition bridges carry about 103,912 daily vehicle crossings. Poor condition does not mean unsafe; bridges judged unsafe are closed or restricted by transportation agencies.
How the Score Breaks Down
| Factor | Weight | County Value | Penalty |
|---|---|---|---|
| Poor-condition bridge share | 40 | 5.0% | 10.0 |
| Poor-condition traffic exposure | 25 | 7.5% of measured traffic | 5.6 |
| Scour-critical bridge share | 20 | 3.8% | 7.5 |
| Average age vs national baseline | 10 | 64 years vs 48 nationally | 6.4 |
| Traffic-data completeness | 5 | 1,380,152 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 | 5.0% |
| State Poor-Condition Share | 4.9% |
| National Poor-Condition Share | 6.7% |
| County Scour-Critical Share | 3.8% |
| Average Bridge Age | 64 years |
| Poor-Condition Traffic Exposure | 103,912 vehicles/day |
Bridges to Watch
Top Bridges to Watch in Napa County
| Bridge | Reason | Condition | Daily Traffic | Year Built |
|---|---|---|---|---|
| State Route 29 over Nvrr Napa River Stanly | Poor condition + traffic exposure | Poor | 48,000 | 1977 |
| State Route 29 over Garnett Creek | Poor condition + traffic exposure | Poor | 12,000 | 1902 |
| Dry CR RD over Dry Creek | Poor condition + traffic exposure | Poor | 2,490 | 1920 |
| State Route 29 SB over Suscol Creek | Poor condition + traffic exposure | Poor | 32,500 | 1981 |
| Knoxv-berryessa RD over Pope Crk.(lake Berryessa | Poor condition + traffic exposure | Poor | 3,570 | 1957 |
| Deer Park Road over Napa River | Poor condition + traffic exposure | Poor | 3,115 | 1966 |
| State Route 128 over Hopper Slough | Poor condition + traffic exposure | Poor | 2,075 | 1921 |
| Greenwood AVE over Garnett Creek | Poor condition + traffic exposure | Poor | 162 | 1904 |
| Trancas ST over Napa River | Scour-critical foundation rating | Fair | 14,755 | 1960 |
| Chiles Pope Vly RD over Chiles Creek | Scour-critical foundation rating | Fair | 1,600 | 1907 |
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.