Total bridges
311
Public highway bridges in Boulder County
County profile · official public datasets
Boulder County, CO
311 public highway bridges tracked in the FHWA National Bridge Inventory: 34.4% rated Good, 63.3% Fair, 2.3% Poor.
- 311
- Public bridges
- 34.4%
- Good condition
- 2.3%
- Poor condition
The verdict
According to the Federal Highway Administration's 2024 National Bridge Inventory.
Boulder County pairs a better-than-median Poor-condition share among rated counties in the state with a newer average build year than the state inventory.
- Top 27%
- lowest Poor share in state
- 2.3%
- Poor-condition share
- 311
- public highway bridges
- 1987
- 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.
Boulder County Bridge Snapshot
According to the Federal Highway Administration's 2024 National Bridge Inventory, Boulder County ranks #17 of 64 Colorado counties with at least 5 public highway bridges on Poor-condition share (lower share ranks better; currently 2.3%). Boulder County, Colorado contains 311 public highway bridges. Roughly 34.4% are rated “Good,” 63.3% “Fair,” and 2.3% “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.
Good condition
34.4%
107 of 311 rated 7-9
Fair condition
63.3%
197 of 311 rated 5-6
Poor condition
2.3%
7 of 311 rated 4 or below
In-state Poor-share rank
#17 of 64
Among Colorado counties with 5+ bridges, lower share ranks better
Condition distribution
Share of 311 NBI-tracked bridges by lowest applicable component rating.
Good 34.4% (107)
Fair 63.3% (197)
Poor 2.3% (7)
Boulder County's Poor-condition bridges carry 54,399 vehicle crossings a day
That is 1.7% of the county's reported daily bridge traffic on 2.3% of its bridges: Poor-condition structures carry less traffic than their share of the inventory. Each Poor bridge averages 7,771 crossings a day against 9,208 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 310 of 311 bridges in this county that report an average daily traffic count. Source: FHWA National Bridge Inventory, 2024 release.
26.4% of Boulder County's bridges have passed the 50-year mark
82 of the 311 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 34.4% 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 33.1% of the county's Poor-condition bridge traffic
US 36 ML WBND over BOULDER CREEK, built 1952, carries 18,000 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 7-bridge count understates how much of the daily burden sits on a single crossing.
Share is of the 54,399 daily crossings on Poor-rated bridges that report a traffic count. Source: FHWA National Bridge Inventory, 2024 release.
When Boulder County's bridges were built
311 bridges with a recorded construction year, grouped by decade
- 1910s 2
1910–1919
2 bridges
- 1920s 4
1920–1929
4 bridges
- 1930s 6
1930–1939
6 bridges
- 1940s 4
1940–1949
4 bridges
- 1950s 21
1950–1959
21 bridges
- 1960s 21
1960–1969
21 bridges
- 1970s
1970–1979
42 bridges
- 1980s
1980–1989
55 bridges
- 1990s
1990–1999
56 bridges
- 2000s
2000–2009
43 bridges
- 2010s
2010–2019
51 bridges
- 2020s 6
2020–2029
6 bridges
What this shows Construction peaked in the 1990s, when 56 of the county's bridges still in the inventory were built, which is 18% of those with a recorded year. That cohort is now 25 to 34 years old in the 2024 inventory. Its average build year is 1987, 5 years newer than the Colorado average of 1982.
How Boulder County compares with Colorado's closest counties by inventory size
The 5 Colorado counties nearest Boulder County in number of bridges, with their condition splits. Its 2.3% Poor share is the 2nd-lowest of these 6. Its average build year of 1987 against a peer-group mean of 1980 is 7 years newer.
Showing the 5 closest of 63 Colorado counties eligible for comparison.
| County | Bridges | Good | Fair | Poor | Avg. built |
|---|---|---|---|---|---|
| Arapahoe County | 391 | 26.1% | 66.8% | 7.2% | 1984 |
| Mesa County | 319 | 35.1% | 63.3% | 1.6% | 1981 |
| Boulder County (this page) | 311 | 34.4% | 63.3% | 2.3% | 1987 |
| Pueblo County | 264 | 29.5% | 65.9% | 4.5% | 1973 |
| Douglas County | 263 | 57.8% | 39.9% | 2.3% | 1996 |
| Las Animas County | 207 | 26.1% | 59.9% | 14% | 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 Boulder 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 Boulder County, both outside Colorado so the neighborhoods are not the same-state size table above.
Similar inventory size
Nearest county inventories outside CO (311 bridges here).
- Madison County, MS · 311 bridges
- Bronx County, NY · 311 bridges
- Huron County, OH · 311 bridges
- Saline County, NE · 312 bridges
Similar average build year
Nearest mean year-built outside CO (1987 here).
- St. Louis County, MO · avg 1987 · 912 bridges
- Ellis County, TX · avg 1987 · 691 bridges
- St. Louis County, MN · avg 1987 · 663 bridges
- Palm Beach County, FL · avg 1987 · 610 bridges
Source: FHWA National Bridge Inventory, 2024 release. Peers floor at 10 bridges so stub inventories cannot own the match.
Fair-condition bridges (197)
Valmont Rd (CR 52)
FairOver: South Boulder Creek
0.4 Mi E of 55th St., Boulder, CO
Built 2006 Load: 39.2 t ADT: 15,236
SH 119 N/EBND
FairOver: FOUR MILE CREEK
IN BOULDER, Boulder, CO
Built 1958 Load: 39.5 t ADT: 4,800
EMMA ST.
FairOver: US 287 ML
IN LAFAYETTE, Boulder, CO
Built 1994 Load: 39.6 t ADT: 3,969
SH 119 ML
FairOver: NORTH BEAVER CREEK
IN NEDERLAND, Boulder, CO
Built 1948 Load: 40.6 t ADT: 4,000
SH 157 ML
FairOver: WALNUT STREET
IN BOULDER, Boulder, CO
Built 1981 Load: 40.9 t ADT: 43,000
Prospect Road CR24
FairOver: Boulder Feeder Ditch
0.3 Mi E of Co Rd 57, Boulder, CO
Built 1988 Load: 41.3 t ADT: 180
17th Street
FairOver: Boulder Creek
0.4 Mi So of Canyon Blvd., Boulder, CO
Built 1985 Load: 41.5 t ADT: 7,658
SH 7 (ARAPAHOE)
FairOver: BIKE/PED UNDERPASS
EAST OF JCT SH 7 & SH, Boulder, CO
Built 2006 Load: 42.1 t ADT: 29,000
SH 119 ML WBND
FairOver: ST. VRAIN RIVER
NEAR LONGMONT, Boulder, CO
Built 2003 Load: 42.4 t ADT: 12,000
Pearl Parkway
FairOver: North Goose Creek
0.6 M E of Foothills Pkwy, Boulder, CO
Built 1986 Load: 42.5 t ADT: 8,372
Deerwood Drive
FairOver: Oligarchy Ditch
20 Ft W of Co Rd 1, Boulder, CO
Built 2000 Load: 42.6 t ADT: 1,709
Hover Road
FairOver: St. Vrain River
100 Ft S of 3rd Avenue, Boulder, CO
Built 1960 Load: 42.8 t ADT: 26,762
SH 93 ML
FairOver: PEDESTRIAN UNDERPASS
BROADWAY AT COLLEGE BLVD, Boulder, CO
Built 1992 Load: 44.3 t ADT: 27,000
County Road 84S
FairOver: South St. Vrain Creek
0.1 Mi S of St Hwy 7, Boulder, CO
Built 1990 Load: 44.6 t ADT: 637
County Road 128E
FairOver: North Boulder Creek
3.9 Mi E of St Hwy 72, Boulder, CO
Built 1994 Load: 45.3 t ADT: 80
County Road 124E
FairOver: North Boulder Creek
0.1 Mi NE of St Hwy 7, Boulder, CO
Built 1994 Load: 46.0 t ADT: 214
North 55th Street
FairOver: Boulder Creek
0.1 Mi N of Flatiron Pkwy, Boulder, CO
Built 1985 Load: 46.1 t ADT: 11,600
SH 93 ML
FairOver: COAL CREEK
3.5 MI NO OF JCT SH 72, Boulder, CO
Built 1965 Load: 46.4 t ADT: 16,000
Airport Road
FairOver: Dry Creek
0.1 Mi N of Buckthorn Dr., Boulder, CO
Built 1994 Load: 46.6 t ADT: 11,244
County Road 71
FairOver: North St. Vrain Creek
30 Ft So of US Hwy 36, Boulder, CO
Built 1991 Load: 47.0 t ADT: 178
CR124E-Hummer Dr.
FairOver: North Boulder Creek
1.2 Mi NE of St Hwy 73, Boulder, CO
Built 1994 Load: 47.7 t ADT: 135
SH 7 ML
FairOver: NORTH ST VRAIN CREEK
IN LYONS, Boulder, CO
Built 1955 Load: 47.8 t ADT: 2,600
SH 7 ML
FairOver: SOUTH BOULDER CREEK
IN BOULDER, Boulder, CO
Built 1938 Load: 48.5 t ADT: 25,000
SH 52 ML
FairOver: WHITE ROCK BOULDER DITCH
NIWOT AT 79th ST INT, Boulder, CO
Built 1965 Load: 49.4 t ADT: 8,900
County Road 35
FairOver: St. Vrain Creek
0.2 Mi S of Co Rd 10, Boulder, CO
Built 1996 Load: 52.3 t ADT: 78
Airport Road CR25
FairOver: Left Hand Creek
50 Ft N of St Hwy 119, Boulder, CO
Built 2003 Load: 54.2 t ADT: 10,085
Airport Road
FairOver: St. Vrain River Overflow
0.2 Mi N of St Vrain Rd, Boulder, CO
Built 2006 Load: 54.2 t ADT: 13,131
SH 119 ML SBND
FairOver: BEASLEY DITCH
@ 55TH ST NE OF BOULDER, Boulder, CO
Built 1971 Load: 54.4 t ADT: 22,000
Airport Road
FairOver: Lykins Gulch
500 ft N of Rogers Road, Boulder, CO
Built 2006 Load: 57.2 t ADT: 13,906
County Road 132
FairOver: Boulder Creek
75 Ft S of St Hwy 119, Boulder, CO
Built 1935 Load: 57.4 t ADT: 846
SH 7 ML
FairOver: NORTH ST VRAIN CREEK
10 MI SE OF ESTES PARK, Boulder, CO
Built 1973 Load: 60.1 t ADT: 1,800
Horizon Avenue
FairOver: Rock Creek
.1 MI East 120th, Boulder, CO
Built 2000 Load: 64.8 t ADT: 1,043
9th Street
FairOver: Boulder Creek
0.08 Mi N of Arapahoe Ave, Boulder, CO
Built 1978 Load: 67.0 t ADT: 14,000
US 287 ML
FairOver: DRAW
IN BOULDER COUNTY, Boulder, CO
Built 1994 Load: 68.0 t ADT: 39,000
US 287 ML
FairOver: HIGHLAND DITCH
2.1 MI NO OF JCT SH 66, Boulder, CO
Built 1999 Load: 70.1 t ADT: 23,000
Cherryvale Road
FairOver: Davidson Ditch
0.9 Mi S of US Hwy 36, Boulder, CO
Built 1986 Load: 73.6 t ADT: 3,123
SH 119 SBND
FairOver: BEASLEY DITCH
Adjacent to Jay Rd, Boulder, CO
Built 1971 Load: 79.1 t ADT: 22,000
SH 119 ML
FairOver: NORTH BOULDER CREEK
7.7 MI E OF JCT SH 72, Boulder, CO
Built 1948 Load: 89.8 t ADT: 3,200
SH 157 ML
FairOver: WONDERLAND CREEK
IN BOULDER, Boulder, CO
Built 1987 Load: 89.8 t ADT: 34,000
SH 157 ML
FairOver: BOULDER WHITEROCK DITCH
IN BOULDER, Boulder, CO
Built 1987 Load: 89.8 t ADT: 34,000
SH 119 ML
FairOver: MIDDLE BOULDER CREEK
IN NEDERLAND, Boulder, CO
Built 1933 Load: 89.8 t ADT: 5,800
SH 42 ML
FairOver: COAL CREEK
3.3 MI SE OF JCT SH 7, Boulder, CO
Built 1967 Load: 89.8 t ADT: 11,000
SH 157 ML
FairOver: SOUTH GOOSE CREEK
0.03 MI N OF PEARL ST, Boulder, CO
Built 1986 Load: 99.9 t ADT: 42,000
SH 157 ML
FairOver: NORTH GOOSE CREEK
0.05 MI N OF PEARL ST., Boulder, CO
Built 1986 Load: 99.9 t ADT: 42,000
SH 128 ML
FairOver: COAL CREEK
0.4 MI E OF JCT SH 93, Boulder, CO
Built 1967 Load: 99.9 t ADT: 4,100
Coalton Drive
FairOver: Rock Creek
0.15 Mi East of McCaslin, Boulder, CO
Built 2000 Load: 99.9 t ADT: 4,964
Indiana Avenue
FairOver: Rock Creek
150 Ft N of Coalton D, Boulder, CO
Built 1999 Load: 99.9 t ADT: 1,916
Read our methodology - how this data is sourced, computed, and verified.
Related
Data sourced from official public datasets. See our methodology for details. Retrieved and formatted by PlainBridges
Every figure on PlainBridges is rendered directly from federal source data, no number is typed in by an editor. This page draws directly on federal source data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. NBI condition categories reflect the latest reported inventory record, not a live safety, closure, or travel decision.