County profile · official public datasets

Lake County, CA

129 public highway bridges tracked in the FHWA National Bridge Inventory: 30.2% rated Good, 62% Fair, 7.8% Poor.

129
Public bridges: 30.2%
Good condition: 7.8%
Poor condition

The verdict

According to the Federal Highway Administration's 2024 National Bridge Inventory.

Lake County posts a higher-than-median Poor-condition share among rated counties in the state across mid-size county bridge inventory.

37th
of 58 on Poor share: 7.8%
Poor-condition share: 129
public highway bridges: 1970
avg year built

Poor is an FHWA condition category from the lowest applicable component rating (4 or below), not a live crossing-safety or closure decision. Rankings cover counties with at least five public highway bridges.

Lake County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Lake County ranks #37 of 58 California counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.8%). Lake County, California contains 129 public highway bridges. Roughly 30.2% are rated “Good,” 62% “Fair,” and 7.8% “Poor.” Poor means the lowest applicable deck, superstructure, substructure, or culvert rating is 4 or below on the 0–9 NBI scale. It is a condition category, not a live safety or closure decision.

Responsible agencies inspect covered bridges on risk-based intervals under current NBIS rules and submit inventory data to FHWA annually. The list below shows every NBI-tracked bridge in the county. Use the “Sort by” controls to change the ordering, and click any row for its reported inspection date, traffic count, and condition fields.

Source: FHWA National Bridge Inventory. See methodology for full definitions.

Total bridges

129

Public highway bridges in Lake County

Good condition

30.2%

39 of 129 rated 7-9

Fair condition

62%

80 of 129 rated 5-6

Poor condition

7.8%

10 of 129 rated 4 or below

In-state Poor-share rank

#37 of 58

Among California counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 129 NBI-tracked bridges by lowest applicable component rating.

Good

30.2% (39)

Fair

62% (80)

Poor

7.8% (10)

Lake County's Poor-condition bridges carry 1,538 vehicle crossings a day

That is 0.5% of the county's reported daily bridge traffic on 7.8% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 154 crossings a day against 3,412 for a Good-condition one. A Poor rating is a condition category, not a closure or a live safety judgement; it means the lowest applicable component rating is 4 or below.

Computed over the 129 of 129 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

69.8% of Lake County's bridges have passed the 50-year mark

90 of the 129 bridges with a recorded construction year were built in 1974 or earlier. Age alone is not a defect: a well-maintained older bridge can rate Good, and 30.2% of this county's inventory does. Even so, this older cohort is the population from which future Poor ratings are drawn, which is why the age profile below matters alongside the condition split above.

Cutoff derives from the 2024 release year minus a 50-year design life. Source: FHWA National Bridge Inventory, 2024 release.

One structure carries 22.8% of the county's Poor-condition bridge traffic

ROAD M1 over EEL RIVER, built 1971, carries 350 vehicles a day, the most of any Poor-rated structure here. The county's Poor-condition exposure is concentrated rather than evenly spread, so the 10-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 1,538 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1900s

1
1920s

2
1930s

11
1940s

8
1950s

16
1960s

33
1970s

23
1980s

10
1990s

8
2000s

5
2010s

10
2020s

2

What this shows Construction peaked in the 1960s, when 33 of the county's bridges still in the inventory were built, which is 25.6% of those with a recorded year. That cohort is now 55 to 64 years old in the 2024 inventory. Its average build year (1970) matches the California average (1970).

How Lake County compares with California's closest counties by inventory size

The 5 California counties nearest Lake County in number of bridges, with their condition splits. Its 7.8% Poor share is the 3rd-lowest of these 6. Its average build year of 1970 against a peer-group mean of 1968 is in line with the group.

Showing the 5 closest of 57 California counties eligible for comparison.

Bridge inventory size and condition shares for Lake County and the 5 California counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
San Francisco County	143	34.3%	51%	14.7%	1969
Nevada County	135	45.2%	40.7%	14.1%	1972
Lake County (this page)	129	30.2%	62%	7.8%	1970
Yuba County	127	37.8%	55.9%	6.3%	1967
Tuolumne County	125	36%	56.8%	7.2%	1964
Sutter County	121	33.9%	52.9%	13.2%	1968

Each share is of that county's own total tracked bridges; peers are the counties with 5 or more bridges whose inventory size is closest to Lake County's. Source: FHWA National Bridge Inventory, 2024 release.

Nationwide counties with similar inventory size or average build year

Two NBI-derived peer sets for Lake County, both outside California so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside CA (129 bridges here).

Clay County, AL · 129 bridges
Cross County, AR · 129 bridges
Lincoln County, CO · 129 bridges
Martin County, FL · 129 bridges

Similar average build year

Nearest mean year-built outside CA (1970 here).

Hamilton County, OH · avg 1970 · 783 bridges
Yavapai County, AZ · avg 1970 · 543 bridges
Garfield County, OK · avg 1970 · 504 bridges
Somerset County, NJ · avg 1970 · 397 bridges

Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.

All 129 Good 39 Fair 80 Poor 10

All bridges (129)

Sort:

Lake County Bridge Snapshot

Condition distribution

Lake County's Poor-condition bridges carry 1,538 vehicle crossings a day

69.8% of Lake County's bridges have passed the 50-year mark

One structure carries 22.8% of the county's Poor-condition bridge traffic

How Lake County compares with California's closest counties by inventory size

Nationwide counties with similar inventory size or average build year

Similar inventory size

Similar average build year

All bridges (129)

ISLAND DR

HILDERBRAND DR

MATHEWS ROAD

FOARD RD

HIGHLAND SPRING RD

ACKLEY RD

SODA BAY RD

DRY CREEK RD

HARBIN SPRINGS RD

MOCKINGBIRD LANE

PARNUM ROAD (US20

STATE ROUTE 29

STATE ROUTE 29

PERINI ROAD

ROAD M01

ROAD M1

STATE ROUTE 29

HARBIN SPRINGS RD

ROAD 16N30

ROAD M1

S COW MTN -8 MILE

CHALK MTN RD

34013: HUNTING CRE

WOLF CREEK ROAD

BARTLETT SPRNGS RD

BIG CANYON ROAD

BIG CANYON ROAD

ELK MOUNTAIN RD

BIG CANYON RD

Related