US Bridges

I-39 & US 51 SB over Blackhawk RD

Fair

Winnebago County, Illinois · 1.75 MI S of US 20 · Structure no. 101014200000000

Built
1981
44 years old
Condition
Fair
inspected December 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
146 ft
1 main span
Daily traffic
14,500
2023 count
Owner
State
State Highway Agency

About this bridge

I-39 & US 51 SB over Blackhawk RD is a steel stringer/multi-beam or girder carrying I-39 & US 51 SB over Blackhawk RD in Winnebago County, Illinois. It was built in 1981, so it is 44 years old, younger than the Illinois average of 45.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 6 out of 9. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

It carries about 14,500 vehicles a day, roughly 37% of them trucks, projected to reach 15,958 by 2046. The structure is 146 ft (44.5 m) long and 42 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-39 & US 51 SB
CrossesBlackhawk RD
Location1.75 MI S of US 20
RouteInterstate 39
CountyWinnebago County
StateIllinois
Coordinates42.19479, -89.02373
Functional classUrban Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionDecember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating98.2 US tons
Inventory rating58.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHS 20
Structure length146 ft (44.5 m)
Longest span87 ft (26.5 m)
Deck width42 ft (12.8 m)
Roadway width38 ft (11.7 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic14,500 (2023)
Projected traffic15,958 by 2046
Trucks37%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I-39 & US 51 SB over Blackhawk RD built?

It was built in 1981, making it 44 years old in 2025.

What condition is I-39 & US 51 SB over Blackhawk RD in?

The National Bridge Inventory rates it in fair condition. The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound. The last reported inspection was in December 2024.

How much traffic does I-39 & US 51 SB over Blackhawk RD carry?

About 14,500 vehicles per day (2023 count), of which roughly 37% are trucks.

How long is I-39 & US 51 SB over Blackhawk RD?

The structure is 146 ft (44.5 m) long with a longest span of 87 ft (26.5 m) and a deck 42 ft wide.

Who owns I-39 & US 51 SB over Blackhawk RD?

It is owned by the State Highway Agency.