County profile · official public datasets

San Juan County, NM

174 public highway bridges tracked in the FHWA National Bridge Inventory: 36.8% rated Good, 56.9% Fair, 6.3% Poor.

174
Public bridges: 36.8%
Good condition: 6.3%
Poor condition

The verdict

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

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

24th
of 32 on Poor share: 6.3%
Poor-condition share: 174
public highway bridges: 1977
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.

San Juan County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, San Juan County ranks #24 of 32 New Mexico counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 6.3%). San Juan County, New Mexico contains 174 public highway bridges. Roughly 36.8% are rated “Good,” 56.9% “Fair,” and 6.3% “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

174

Public highway bridges in San Juan County

Good condition

36.8%

64 of 174 rated 7-9

Fair condition

56.9%

99 of 174 rated 5-6

Poor condition

6.3%

11 of 174 rated 4 or below

In-state Poor-share rank

#24 of 32

Among New Mexico counties with 5+ bridges, lower share ranks better

Condition distribution

Share of 174 NBI-tracked bridges by lowest applicable component rating.

Good

36.8% (64)

Fair

56.9% (99)

Poor

6.3% (11)

San Juan County's Poor-condition bridges carry 27,547 vehicle crossings a day

That is 2.7% of the county's reported daily bridge traffic on 6.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 2,504 crossings a day against 5,347 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 174 of 174 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

35.6% of San Juan County's bridges have passed the 50-year mark

62 of the 174 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 36.8% 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 59.6% of the county's Poor-condition bridge traffic

IRR/US64/491 WBL over SAN JUAN RIVER, built 1936, carries 16,419 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 11-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 27,547 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

3
1930s

9
1940s

9
1950s

13
1960s

20
1970s

49
1980s

26
1990s

14
2000s

17
2010s

12
2020s

2

What this shows Construction peaked in the 1970s, when 49 of the county's bridges still in the inventory were built, which is 28.2% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1977) matches the New Mexico average (1973).

How San Juan County compares with New Mexico's closest counties by inventory size

The 5 New Mexico counties nearest San Juan County in number of bridges, with their condition splits. Its 6.3% Poor share is the 4th-lowest of these 6. Its average build year of 1977 against a peer-group mean of 1971 is 6 years newer.

Showing the 5 closest of 31 New Mexico counties eligible for comparison.

Bridge inventory size and condition shares for San Juan County and the 5 New Mexico counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Socorro County	188	16.5%	76.1%	7.4%	1961
Sandoval County	182	40.7%	54.4%	4.9%	1979
San Miguel County	175	41.1%	50.9%	8%	1972
San Juan County (this page)	174	36.8%	56.9%	6.3%	1977
Rio Arriba County	160	47.5%	46.3%	6.3%	1973
Colfax County	140	37.9%	57.1%	5%	1969

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 San Juan 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 San Juan County, both outside New Mexico so the neighborhoods are not the same-state size table above.

Similar inventory size

Nearest county inventories outside NM (174 bridges here).

Hempstead County, AR · 174 bridges
Eagle County, CO · 174 bridges
Washington County, IN · 174 bridges
Lac qui Parle County, MN · 174 bridges

Similar average build year

Nearest mean year-built outside NM (1977 here).

San Diego County, CA · avg 1977 · 1,632 bridges
King County, WA · avg 1977 · 1,238 bridges
Riverside County, CA · avg 1977 · 1,117 bridges
Shelby County, TN · avg 1977 · 1,077 bridges

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

All 174 Good 64 Fair 99 Poor 11

Fair-condition bridges (99)

Sort:

San Juan County Bridge Snapshot

Condition distribution

San Juan County's Poor-condition bridges carry 27,547 vehicle crossings a day

35.6% of San Juan County's bridges have passed the 50-year mark

One structure carries 59.6% of the county's Poor-condition bridge traffic

How San Juan County compares with New Mexico'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 (99)

FL-4359

US-64

US-550

45Z008

US-550

US-64

IRR BIA RTE N5

IRR BIA RTE N13

IRR BIA RTE N13

IRR BIA RTE N36

IRR BIA RTE N5000

IRR BIA RTE N12

FL-2500

45-1120

45-350

IRR BIA RTE N364

IRR BIA RTE 3003

IRR BIA RTE N4002

IRR BIA RTE N3003

IRR BIA RTE N4022

IRR BIA RTE N4022

IRR BIA RTE N4030

IRR BIA RTE N4065

IRR BIA RTE N4028

IRR BIA RTE N4022

US-491

LOOP ROAD

NM-173

IRR BIA RTE 4063

IRR/US-491

NM-371

US-64

IRR BIA RTE N5000

IRR BIA RTE N33

FR-6662

IRR BIA RTE N9652

NM-5001

US-64

IRR BIA RTE N3002

IRR BIA RTE N5000

NM-371

IRR/US-64

NM-511

IRR BIA RTE N36

IRR BIA RTE 4178

45-3000

SUBDIVISION ACCESS

IRR BIA RTE N3005

GALLO WASH ROAD

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