County profile · official public datasets

Colusa County, CA

211 public highway bridges tracked in the FHWA National Bridge Inventory: 40.8% rated Good, 52.1% Fair, 7.1% Poor.

211
Public bridges: 40.8%
Good condition: 7.1%
Poor condition

The verdict

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

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

32nd
of 58 on Poor share: 7.1%
Poor-condition share: 211
public highway bridges: 1968
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.

Colusa County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Colusa County ranks #32 of 58 California counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 7.1%). Colusa County, California contains 211 public highway bridges. Roughly 40.8% are rated “Good,” 52.1% “Fair,” and 7.1% “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

211

Public highway bridges in Colusa County

Good condition

40.8%

86 of 211 rated 7-9

Fair condition

52.1%

110 of 211 rated 5-6

Poor condition

7.1%

15 of 211 rated 4 or below

In-state Poor-share rank

#32 of 58

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

Condition distribution

Share of 211 NBI-tracked bridges by lowest applicable component rating.

Good

40.8% (86)

Fair

52.1% (110)

Poor

7.1% (15)

Colusa County's Poor-condition bridges carry 6,880 vehicle crossings a day

That is 0.9% of the county's reported daily bridge traffic on 7.1% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 459 crossings a day against 5,083 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 211 of 211 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

66.8% of Colusa County's bridges have passed the 50-year mark

141 of the 211 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 40.8% 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 30.2% of the county's Poor-condition bridge traffic

LONE STAR ROAD over CORTINA CREEK, built 1968, carries 2,077 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 15-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 6,880 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1910s

7
1920s

9
1930s

16
1940s

6
1950s

11
1960s

40
1970s

78
1980s

11
1990s

8
2000s

18
2010s

7

What this shows Construction peaked in the 1970s, when 78 of the county's bridges still in the inventory were built, which is 37% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1968) matches the California average (1970).

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

The 5 California counties nearest Colusa County in number of bridges, with their condition splits. Its 7.1% Poor share is the 3rd-lowest of these 6. Its average build year of 1968 against a peer-group mean of 1965 is in line with the group.

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

Bridge inventory size and condition shares for Colusa County and the 5 California counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Glenn County	242	36.8%	52.9%	10.3%	1954
Colusa County (this page)	211	40.8%	52.1%	7.1%	1968
Marin County	207	43.5%	46.9%	9.7%	1958
Trinity County	194	56.2%	39.7%	4.1%	1977
El Dorado County	192	46.9%	46.9%	6.3%	1975
Santa Cruz County	192	40.1%	42.2%	17.7%	1963

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 Colusa 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 Colusa County, both outside California so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside CA (211 bridges here).

Charlotte County, FL · 211 bridges
Kemper County, MS · 211 bridges
Pike County, MS · 211 bridges
Barton County, MO · 211 bridges

Similar average build year

Nearest mean year-built outside CA (1968 here).

Montgomery County, PA · avg 1968 · 828 bridges
Providence County, RI · avg 1968 · 476 bridges
Delaware County, PA · avg 1968 · 387 bridges
Genesee County, MI · avg 1968 · 371 bridges

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

All 211 Good 86 Fair 110 Poor 15

Fair-condition bridges (110)

Sort:

Colusa County Bridge Snapshot

Condition distribution

Colusa County's Poor-condition bridges carry 6,880 vehicle crossings a day

66.8% of Colusa County's bridges have passed the 50-year mark

One structure carries 30.2% of the county's Poor-condition bridge traffic

How Colusa 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

Fair-condition bridges (110)

INTERSTATE 5 NB

DIRKS ROAD

STATE ROUTE 45

INTERSTATE 5

STATE ROUTE 20

FRESHWATER ROAD

GRIDLEY ROAD

LODOGA-SITES RD

SITES-LODOGA ROAD

SAN JOSE ROAD

FOUR MILE ROAD

SAN JOSE ROAD

WILBUR SPRINGS RD

GIBSON ROAD

FAIRVIEW ROAD

MCDERMOTT ROAD

OHM RD

LONE STAR ROAD

LENAHAN ROAD

STATE ROUTE 16

LEESVILLE ROAD

HARRINGTON ROAD

INTERSTATE 5 SB

INTERSTATE 5 NB

ABEL ROAD

GREENBAY ROAD

GAIL AVE (OLD 99W)

INTERSTATE 5 SB

MEYERS ROAD

EDDY ROAD

LA GRANDE RD

LODOGA-STONYFRD RD

TWO MILE ROAD

FIFTH ST (OLD 99W)

MAXWELL-SITES RD

DELEVAN ROAD

MAXWELL ROAD

INTERSTATE 5

INTERSTATE 5

DELPHOS RD

STATE ROUTE 20

DANLEY ROAD

INTERSTATE 5

INTERSTATE 5 SB

INTERSTATE 5 NB

TWO MILE ROAD

CLARK AVENUE

BRIM ROAD

BEAR VALLEY ROAD

FAIRVIEW ROAD

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