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)
Co Rd 54A
FairOver: Middle Boulder Creek
Castle Rock Pull Off, Boulder, CO
Built 1917 Load: 6.6 t ADT: 66
BOULDER CREEK PATH
FairOver: BOULDER CREEK
4Mi Canyon Path at SH119, Boulder, CO
Built 2020 Load: 8.0 t ADT: 11
SH 157 ML
FairOver: PEARL STREET
2.9 MI N OF US 36, Boulder, CO
Built 1985 Load: 8.2 t ADT: 43,000
SH 157 ML
FairOver: BNSF RR
IN BOULDER, Boulder, CO
Built 1981 Load: 10.9 t ADT: 43,000
Oxford Rd (Cr 26)
FairOver: Boulder Feeder Ditch
0.3 Mi W of Co Rd 41, Boulder, CO
Built 1950 Load: 13.4 t ADT: 422
SH 93 ML
FairOver: SOUTH BOULDER CREEK
0.4 MI N OF JCT SH 170 +, Boulder, CO
Built 1969 Load: 14.0 t ADT: 17,000
US 36 ML EBND
FairOver: BOULDER CREEK
IN BOULDER, Boulder, CO
Built 1960 Load: 15.0 t ADT: 18,000
US 287 ML
FairOver: DRY CREEK
Ken Pratt Blvd-Longmont, Boulder, CO
Built 1947 Load: 16.5 t ADT: 22,000
SH 119 ML
FairOver: BOULDER CREEK
13.7 MI E OF JCT SH 72, Boulder, CO
Built 1953 Load: 17.1 t ADT: 6,400
SH170 ML(McCaslin)
FairOver: US 36 ML
3.9 MI E OF JCT SH 93, Boulder, CO
Built 1983 Load: 17.5 t ADT: 24,000
SH 119 ML
FairOver: BOULDER CREEK
JUST WEST OF BOULDER, Boulder, CO
Built 1953 Load: 18.1 t ADT: 6,400
120TH STREET
FairOver: Rock Creek
0.5 Mi S of S. Boulder Rd, Boulder, CO
Built 1986 Load: 18.2 t ADT: 3,390
County Road 47
FairOver: St. Vrain Supply Canal
2.7 Mi N of St Hwy 66, Boulder, CO
Built 1997 Load: 18.7 t ADT: 316
County Road 130
FairOver: Middle Boulder Creek
2.5 Mi W of St Hwy 72, Boulder, CO
Built 1990 Load: 19.4 t ADT: 742
Rogers Road
FairOver: Lykin Gulch
0.25 Mi W of Airport Rd, Boulder, CO
Built 2000 Load: 20.9 t ADT: 80
SH 72 ML
FairOver: MIDDLE ST VRAIN CREEK
7 MI NORTH OF WARD, Boulder, CO
Built 1959 Load: 21.0 t ADT: 1,400
SH 170 ML
FairOver: SOUTH BOULDER CREEK
0.9 MI W. OF EL DORADO SP, Boulder, CO
Built 1930 Load: 21.0 t ADT: 388
SH 7 ML
FairOver: BEAR CANYON CREEK
JCT 157 & ARAPAHOE, Boulder, CO
Built 1985 Load: 22.4 t ADT: 29,000
Folsom Street
FairOver: Goose Creek
300 Ft. So. of Valmont, Boulder, CO
Built 1970 Load: 22.6 t ADT: 10,980
US 287 ML
FairOver: LEFT HAND CREEK
IN LONGMONT, Boulder, CO
Built 1948 Load: 22.6 t ADT: 24,000
St Vrain Road CR16
FairOver: Boulder Feeder Ditch
0.5 Mi E of Co Rd 51, Boulder, CO
Built 1955 Load: 22.7 t ADT: 1,009
SH 170 ML
FairOver: COMMUNITY DITCH
E ENT ELDORADO STATE PARK, Boulder, CO
Built 1999 Load: 22.7 t ADT: 1,300
55th Street
FairOver: Empson Ditch
250 Ft N of Penn. Ave., Boulder, CO
Built 1996 Load: 23.1 t ADT: 9,146
US 36 ML
FairOver: FOUR MILE CANYON CREEK
28th ST in BOULDER, Boulder, CO
Built 1957 Load: 23.2 t ADT: 16,000
US 36 ML
FairOver: SUPPLY DITCH
IN LYONS, Boulder, CO
Built 1972 Load: 23.2 t ADT: 15,000
FDR 298 & BC 116
FairOver: NORTH BOULDER CREEK
3.45 MI SW OF CO HWY 72, Boulder, CO
Built 1970 Load: 23.3 t ADT: 40
SH 157 ML
FairOver: BEAR CANYON CREEK
NEAR COLORADO AVE., Boulder, CO
Built 1978 Load: 24.2 t ADT: 38,000
C. R. 41 (63rd St)
FairOver: St. Vrain Creek
0.5 Mi N of Co Rd 10, Boulder, CO
Built 1991 Load: 24.3 t ADT: 134
Boston Ave (Cr 18)
FairOver: St. Vrain Creek
0.1 Mi E of Co Rd 15, Boulder, CO
Built 1990 Load: 24.4 t ADT: 9,636
Brockway Drive
FairOver: Goodhue Ditch
0.1 Mi E of 76th Street, Boulder, CO
Built 1962 Load: 24.5 t ADT: 6,900
Co Rd 54A
FairOver: Middle Boulder Creek
Castle Rock Pull Off, Boulder, CO
Built 1917 Load: 24.5 t ADT: 70
Rock Creek Pkwy.
FairOver: Rock Creek
0.3 Mi N of Coalton D, Boulder, CO
Built 1999 Load: 24.5 t ADT: 11,360
SH 72 ML
FairOver: SOUTH ST VRAIN CREEK
3.8 MI NORTH OF WARD, Boulder, CO
Built 1959 Load: 24.6 t ADT: 1,100
COUNTY ROAD 116
FairOver: BOULDER CREEK
3.3 MI WEST OF ST HWY 72, Boulder, CO
Built 1995 Load: 25.1 t ADT: 74
SH 170 ML
FairOver: DAVIDSON DITCH
1.5 MI W OF JCT SH 93, Boulder, CO
Built 1952 Load: 25.4 t ADT: 1,200
County Road 31
FairOver: St. Vrain Creek
0.6 Mi S of Co Rd 10, Boulder, CO
Built 1979 Load: 25.5 t ADT: 6,233
SH 93 ML
FairOver: BOULDER CREEK
N. of Arapahoe Ave, Boulder, CO
Built 2004 Load: 25.6 t ADT: 22,000
US 36 ML
FairOver: CANYON CREEK
IN BOULDER, Boulder, CO
Built 1951 Load: 25.7 t ADT: 45,000
SH 119 ML
FairOver: OLIGARCHY DITCH
IN LONGMONT, Boulder, CO
Built 2004 Load: 25.9 t ADT: 24,000
SH 157 ML
FairOver: BNSF RR
IN BOULDER, Boulder, CO
Built 1988 Load: 26.5 t ADT: 34,000
SH 7 ML EBND
FairOver: BOULDER CREEK
ARAPAHOE AVENUE, Boulder, CO
Built 1966 Load: 27.3 t ADT: 15,000
County Road 84W
FairOver: North St. Vrain Creek
1.0 Mi NW of St Hwy 7, Boulder, CO
Built 1927 Load: 27.6 t ADT: 122
County Road 84S
FairOver: South St. Vrain Creek
250 ft S of Hwy 7, Boulder, CO
Built 2019 Load: 27.9 t ADT: 67
N. 61st Street
FairOver: Boulder Creek
1.0 Mi So of Jay Road, Boulder, CO
Built 1986 Load: 28.2 t ADT: 5,789
EBND US 36 ML
FairOver: US 36 SPUR/BASELINE RD
IN BOULDER, Boulder, CO
Built 1963 Load: 28.2 t ADT: 16,500
6th Street
FairOver: Boulder Creek
0.1 Mi So of Canyon Blvd, Boulder, CO
Built 1978 Load: 28.3 t ADT: 10,000
3rd Ave. EB
FairOver: GW RR
.15 Mi W of Jct 119, Boulder, CO
Built 1969 Load: 28.6 t ADT: 7,667
Dillon Road
FairOver: Coal Creek & Ped Tra
0.5 Mi E of McCaslin Blvd, Boulder, CO
Built 1993 Load: 29.1 t ADT: 15,732
SH 7 ML
FairOver: DRAW
0.35 MI E OF 75th ST, Boulder, CO
Built 1928 Load: 29.3 t ADT: 19,000
SH 157 ML SBND
FairOver: S BLDR Rd-TBLE MSA Dr
0.9 MI N OF JCT US 36, Boulder, CO
Built 1973 Load: 29.4 t ADT: 19,000
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.