Boulder County Bridge Report Card

Boulder County scores 89 out of 100 on BridgeLookup's Bridge Condition Exposure Score, based on FHWA National Bridge Inventory records.

B89 / 100

Local infrastructure snapshot

Boulder County, Colorado

Boulder County has 321 bridges in the National Bridge Inventory, with 7 rated poor and 8 rated scour-critical. Its poor-condition share of 2.2% is at or below the 4.6% statewide average. Poor-condition bridges carry about 54,399 daily vehicle crossings.

321Total Bridges

7Poor (2.2%)

211Fair (65.7%)

8Scour-Critical

Quote-Ready Local Facts

2.2%of county bridges are in poor condition, compared with 4.6% statewide and 6.7% nationally.

54,399daily vehicle crossings are on poor-condition bridges in the county.

8bridges are rated scour-critical, or 2.5% of the county bridge inventory.

Copyable Facts for Reporters

BridgeLookup.com gives Boulder County a Bridge Condition Exposure Score of 89/100 (B). The county has 321 bridges in the National Bridge Inventory, including 7 in poor condition and 8 rated scour-critical. Poor-condition bridges carry about 54,399 daily vehicle crossings. Poor condition does not mean unsafe; bridges judged unsafe are closed or restricted by transportation agencies.

Download all county report-card scores as CSV.

How the Score Breaks Down

Factor	Weight	County Value	Penalty
Poor-condition bridge share	40	2.2%	4.4
Poor-condition traffic exposure	25	1.7% of measured traffic	1.3
Scour-critical bridge share	20	2.5%	5.0
Average age vs national baseline	10	38 years vs 48 nationally	0.0
Traffic-data completeness	5	3,231,264 measured daily crossings	0.0

Score = 100 minus weighted penalties. The score is a comparative research signal, not an official safety rating. Read the full methodology.

County Comparisons

County Poor-Condition Share	2.2%
State Poor-Condition Share	4.6%
National Poor-Condition Share	6.7%
County Scour-Critical Share	2.5%
Average Bridge Age	38 years
Poor-Condition Traffic Exposure	54,399 vehicles/day

Bridges to Watch

Busiest Poor-Condition BridgeUS 36 Ml Wbnd over Boulder Creek — 18,000 vehicles/day Oldest Listed BridgeCo RD 54a over Middle Boulder Creek — built in 1917 All County BridgesBrowse every bridge record in Boulder County.

Top Bridges to Watch in Boulder County

Bridge	Reason	Condition	Daily Traffic	Year Built
US 36 Ml Wbnd over Boulder Creek	Poor condition + traffic exposure	Poor	18,000	1952
SH 7 Ml Wbnd over Boulder Creek	Poor condition + traffic exposure	Poor	15,000	1938
3rd AVE WB over Gw Rr	Poor condition + traffic exposure	Poor	9,116	1974
Rock Creek PKWY over Community Ditch	Poor condition + traffic exposure	Poor	7,760	2000
South Bowen Street over Left Hand Creek	Poor condition + traffic exposure	Poor	1,835	1965
No. 30th Street over Four Mile Creek	Poor condition + traffic exposure	Poor	1,424	1973
US 36 Fr RD over Boulder Creek SR	Poor condition + traffic exposure	Poor	1,264	1952
US 36 Ml Ebnd over Boulder Creek	Scour-critical foundation rating	Fair	18,000	1960
US 36 Ml over Four Mile Canyon Creek	Scour-critical foundation rating	Fair	16,000	1957
County Road 84w over North St. Vrain Creek	Scour-critical foundation rating	Fair	122	1927

Important safety note

Poor condition does not mean a bridge is unsafe. It means at least one major component has significant deterioration and the bridge is a priority for maintenance, repair, or replacement. Bridges judged unsafe are closed or restricted by transportation agencies.