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)
Glenwood Drive
FairOver: Two Mile Creek
400 Ft W of State Hwy 36, Boulder, CO
Built 1972 Load: 32.7 t ADT: 3,439
Junction Pl
FairOver: Goose Creek
0.1 mi N of Pearl Pkwy, Boulder, CO
Built 2017 Load: 32.7 t ADT: 1,484
Baseline Road
FairOver: Bear Canyon Creek
300 ft E of Meadow Dr, Boulder, CO
Built 1980 Load: 32.7 t ADT: 14,884
MONROE DRIVE
FairOver: EMPSON DITCH
0.1 Mi S of Colorado Ave., Boulder, CO
Built 2020 Load: 32.7 t ADT: 1,175
EISENHOWER DRIVE
FairOver: EMPSON DITCH
0.5 MI S OF ARAPAHOE AVE, Boulder, CO
Built 1972 Load: 32.7 t ADT: 1,860
SH 93 ML
FairOver: SKUNK CREEK / PED PATH
0.1 MI N of 27th WAY, Boulder, CO
Built 2014 Load: 32.7 t ADT: 20,000
SH 119
FairOver: WONDERLAND CRK AND PATH
.5 MI W OF FOOTHILLS PKWY, Boulder, CO
Built 2006 Load: 32.7 t ADT: 26,000
SOUTH BOULDER RD
FairOver: DRAINAGE DITCH AR
IN LAFAYETTE, Boulder, CO
Built 1996 Load: 32.7 t ADT: 37,000
120TH STREET
FairOver: Coal Creek
0.25 M S of S. Boulder Rd, Boulder, CO
Built 1977 Load: 32.7 t ADT: 8,097
15th Avenue
FairOver: Oligarchy Ditch
100 Ft W of Lamplighte Dr, Boulder, CO
Built 1989 Load: 32.7 t ADT: 450
21st Ave Eastbound
FairOver: Oligarchy Ditch
300 Ft. E of Daley Dr., Boulder, CO
Built 1975 Load: 32.7 t ADT: 4,495
3rd Avenue
FairOver: Oligarchy Ditch
At Pace Street, Boulder, CO
Built 1969 Load: 32.7 t ADT: 16,797
Alpine Street
FairOver: Oligarchy Ditch
100 ft N of E 9th Ave., Boulder, CO
Built 1975 Load: 32.7 t ADT: 3,757
Boston Ave
FairOver: Spring Gulch
0.1 mile E. of Martin St., Boulder, CO
Built 2017 Load: 32.7 t ADT: 978
Dry Creek Drive
FairOver: Dry Creek No. 1
0.1 Mi So of Bent Way, Boulder, CO
Built 1991 Load: 32.7 t ADT: 5,490
E 5th Avenue
FairOver: Oligarchy Ditch
0.1 Mi East of Fox St, Boulder, CO
Built 1970 Load: 32.7 t ADT: 1,321
E 9th Avenue
FairOver: Oligarchy Ditch
100 ft E of Alpine Street, Boulder, CO
Built 2004 Load: 32.7 t ADT: 12,630
Fordham Street
FairOver: Dry Creek
0.3 Mi So of Nelson Road, Boulder, CO
Built 1997 Load: 32.7 t ADT: 1,944
Hover Road
FairOver: Oligarchy Ditch
100 Ft S of 20th Street, Boulder, CO
Built 1990 Load: 32.7 t ADT: 25,769
Hover Road
FairOver: Dry Creek No. 1
0.2 Mi S of Nelson Road, Boulder, CO
Built 1985 Load: 32.7 t ADT: 29,369
Pike Road
FairOver: Left Hand Creek
0.2 Mi E of Sunset St, Boulder, CO
Built 1994 Load: 32.7 t ADT: 13,459
Pratt Parkway
FairOver: BNRR and 1st Avenue
0.2 Mi N of Boston Ave, Boulder, CO
Built 1980 Load: 32.7 t ADT: 11,924
Price/Frontage Rds
FairOver: Dry Creek
S. Sunset St and Hwy 11, Boulder, CO
Built 1984 Load: 32.7 t ADT: 7,332
Spencer Street
FairOver: Oligarchy Ditch
50 Ft So of 20th St, Boulder, CO
Built 1975 Load: 32.7 t ADT: 995
Sunset Way
FairOver: Dry Creek
20 Ft SW of Korte Way, Boulder, CO
Built 1996 Load: 32.7 t ADT: 540
McConnell Drive
FairOver: Saint Vrain Creek
50 Ft S of US36 / SH66, Boulder, CO
Built 2006 Load: 32.7 t ADT: 2,031
SH 157 RAMP
FairOver: US 36 ML
IN BOULDER, Boulder, CO
Built 1971 Load: 32.8 t ADT: 44,000
County Road 1
FairOver: Big Dry Creek
0.3 Mi N of Co Rd 20.5, Boulder, CO
Built 1995 Load: 32.9 t ADT: 9,859
SH 119 ML NB
FairOver: BEASLEY DITCH
@ 55TH ST NE OF BOULDER, Boulder, CO
Built 1958 Load: 33.4 t ADT: 22,000
SH 157 ML
FairOver: SKUNK CREEK
IN BOULDER, Boulder, CO
Built 1978 Load: 33.5 t ADT: 43,000
County Road 80
FairOver: North St. Vrain Creek
0.8 Mi W of US Hwy 36, Boulder, CO
Built 1988 Load: 33.6 t ADT: 199
County Road 80
FairOver: North St. Vrain Creek
20 Ft S of US Hwy 36, Boulder, CO
Built 1988 Load: 34.5 t ADT: 268
Folsom Street
FairOver: Boulder Creek
0.40 Mi S of Canyon Blvd, Boulder, CO
Built 1965 Load: 34.6 t ADT: 8,407
Baseline Road
FairOver: South Boulder Creek
0.1 Mi W of Cherryvale Rd, Boulder, CO
Built 1980 Load: 35.2 t ADT: 4,986
CHERRYVALE ROAD
FairOver: SH 36 ML
1.4 MI E OF JCT SH 157, Boulder, CO
Built 2009 Load: 35.4 t ADT: 5,525
SH 93 ML
FairOver: PED. UNDERPASS
BROADWAY AND 16TH ST., Boulder, CO
Built 2013 Load: 35.6 t ADT: 27,000
SH 157 ML
FairOver: BOULDER CREEK
JUST N. OF HWY 7, Boulder, CO
Built 1981 Load: 35.8 t ADT: 43,000
SH 157 ML
FairOver: SH 119 ML
IN BOULDER, Boulder, CO
Built 1988 Load: 36.5 t ADT: 34,000
McCaslin Blvd
FairOver: Coal Creek
0.3 Mi S of US Hwy 36, Boulder, CO
Built 1995 Load: 36.5 t ADT: 17,606
Flatiron Parkwy
FairOver: Dry Creek
0.1 Mi E of N 55th Street, Boulder, CO
Built 1985 Load: 36.7 t ADT: 2,240
US 36 ML
FairOver: NORTH ST VRAIN CREEK
IN LYONS, Boulder, CO
Built 2007 Load: 36.8 t ADT: 9,000
SH 119 ML NBND
FairOver: LEFT HAND CREEK
3.6 MI NE OF JCT SH 52, Boulder, CO
Built 1959 Load: 37.4 t ADT: 14,000
US 36 ML
FairOver: HIGHLAND CANAL
1.2 MI SE OF JCT SH 7 LYO, Boulder, CO
Built 1972 Load: 37.5 t ADT: 15,000
County Road 38
FairOver: Boulder Creek
1.5 Mi W of Co Rd 901, Boulder, CO
Built 1988 Load: 37.6 t ADT: 1,640
Winding Trail Dr
FairOver: Wonderland Creek
300 ft W of 28th, Boulder, CO
Built 2018 Load: 37.6 t ADT: 632
Arapahoe Avenue
FairOver: Boulder Creek
50 Ft S of Canyon Blvd, Boulder, CO
Built 1990 Load: 38.0 t ADT: 7,200
FDR 112
FairOver: SOUTH ST VRAIN CREEK
5.75 MI WEST OF CO HWY 72, Boulder, CO
Built 1989 Load: 38.2 t ADT: 177
County Road 103
FairOver: Middle St. Vrain Creek
0.5 Mi SW of St Hwy 7, Boulder, CO
Built 1993 Load: 38.8 t ADT: 170
County Road 96
FairOver: South St. Vrain Creek
100 Ft. W of St Hwy 72, Boulder, CO
Built 2000 Load: 39.0 t ADT: 64
US 287 ML
FairOver: LOWER BOULDER DITCH
3.4 MI N OF LAFAYETTE, Boulder, CO
Built 1997 Load: 39.0 t ADT: 26,000
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.