County profile · official public datasets

Summit County, CO

57 public highway bridges tracked in the FHWA National Bridge Inventory: 22.8% rated Good, 71.9% Fair, 5.3% Poor.

57
Public bridges: 22.8%
Good condition: 5.3%
Poor condition

The verdict

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

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

35th
of 64 on Poor share: 5.3%
Poor-condition share: 57
public highway bridges: 1980
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.

Summit County Bridge Snapshot

According to the Federal Highway Administration's 2024 National Bridge Inventory, Summit County ranks #35 of 64 Colorado counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 5.3%). Summit County, Colorado contains 57 public highway bridges. Roughly 22.8% are rated “Good,” 71.9% “Fair,” and 5.3% “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

Public highway bridges in Summit County

Good condition

22.8%

13 of 57 rated 7-9

Fair condition

71.9%

41 of 57 rated 5-6

Poor condition

5.3%

3 of 57 rated 4 or below

In-state Poor-share rank

#35 of 64

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

Condition distribution

Share of 57 NBI-tracked bridges by lowest applicable component rating.

Good

22.8% (13)

Fair

71.9% (41)

Poor

5.3% (3)

Summit County's Poor-condition bridges carry 30,000 vehicle crossings a day

That is 5.5% of the county's reported daily bridge traffic on 5.3% of its bridges: Poor-condition structures carry more traffic than their share of the inventory. Each Poor bridge averages 10,000 crossings a day against 14,689 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 57 of 57 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.

36.8% of Summit County's bridges have passed the 50-year mark

21 of the 57 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 22.8% 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 33.3% of the county's Poor-condition bridge traffic

I 70 ML WBND over CORRAL CREEK, built 1979, carries 10,000 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 3-bridge count understates how much of the daily burden sits on a single crossing.

Share is of the 30,000 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.

1920s

1
1930s

1
1940s

2
1950s

1
1960s

7
1970s

20
1980s

11
1990s

5
2000s

3
2010s

3
2020s

3

What this shows Construction peaked in the 1970s, when 20 of the county's bridges still in the inventory were built, which is 35.1% of those with a recorded year. That cohort is now 45 to 54 years old in the 2024 inventory. Its average build year (1980) matches the Colorado average (1982).

How Summit County compares with Colorado's closest counties by inventory size

The 5 Colorado counties nearest Summit County in number of bridges, with their condition splits. Its 5.3% Poor share is the 5th-lowest of these 6. Its average build year of 1980 against a peer-group mean of 1980 is in line with the group.

Showing the 5 closest of 63 Colorado counties eligible for comparison.

Bridge inventory size and condition shares for Summit County and the 5 Colorado counties closest to it in inventory size
County	Bridges	Good	Fair	Poor	Avg. built
Cheyenne County	61	57.4%	42.6%	0%	1978
Montezuma County	61	27.9%	63.9%	8.2%	1978
San Miguel County	59	54.2%	42.4%	3.4%	1987
Summit County (this page)	57	22.8%	71.9%	5.3%	1980
Park County	55	29.1%	67.3%	3.6%	1975
Rio Blanco County	54	31.5%	66.7%	1.9%	1980

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

Similar inventory size

Nearest county inventories outside CO (57 bridges here).

DeSoto County, FL · 57 bridges
Dodge County, GA · 57 bridges
McIntosh County, GA · 57 bridges
Gem County, ID · 57 bridges

Similar average build year

Nearest mean year-built outside CO (1980 here).

Tulsa County, OK · avg 1980 · 1,135 bridges
Miami-Dade County, FL · avg 1980 · 1,057 bridges
Pulaski County, AR · avg 1980 · 721 bridges
McLennan County, TX · avg 1980 · 714 bridges

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

All 57 Good 13 Fair 41 Poor 3

All bridges (57)

Sort:

Summit County Bridge Snapshot

Condition distribution

Summit County's Poor-condition bridges carry 30,000 vehicle crossings a day

36.8% of Summit County's bridges have passed the 50-year mark

One structure carries 33.3% of the county's Poor-condition bridge traffic

How Summit County compares with Colorado'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 (57)

SLATE CREEK RD

I 70 ML EBND

FRENCH STREET

SHRINE PASS ROAD

E. KEYSTONE RD.

County Road 1813

HAMILTON CREEK RD

I 70 ML EBND

SH 9 ML

I 70 ML EBND

BALD EAGLE ROAD

SH 9 ML

I 70 ML WBND

I 70 ML EBND

SH 9 ML

I 70 ML WBND

I 70 ML EBND

I 70 ML EBND

I70 ML WBND

Heeney Road

MAIN STREET

WEST KEYSTONE RD.

BOULDER CREEK RD

ADAMS AVENUE

SH 9 ML

CREEKSIDE DRIVE

MADISON AVE

4TH AVE-CREEKSIDE

SH 91 ML

STEPHENS STREET

BROKEN LANCE DR

MONTEZUMA RD CR5

PARK AVENUE

I 70 ML EBND

I 70 ML WBND

WILDERNEST ROAD

SWAN MOUNTAIN RD

SH 9 ML

SH 91 ML

US 6 ML

SH 9 ML

SH 9 ML

SH 9 ML

SH 9 ML

US 6 ML

FSR 355.1

REVETT DRIVE

SH 9 ML

I 70 EBND

I 70 WBND

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