US Bridges

I-75 NB over Carp River

Fair

Mackinac County, Michigan · 4.6 MI N of M-123 · Structure no. 000000000005939

Built
1964
61 years old
Condition
Fair
inspected December 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
303 ft
3 main spans
Daily traffic
2,039
2007 count
Owner
State
State Highway Agency

About this bridge

I-75 NB over Carp River is a steel stringer/multi-beam or girder carrying I-75 NB over Carp River in Mackinac County, Michigan. It was built in 1964, so it is 61 years old, older than the Michigan average of 48.3 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 2,039 vehicles a day, roughly 9% of them trucks, projected to reach 5,205 by 2018. The structure is 303 ft (92.3 m) long and 43 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

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CarriesI-75 NB
CrossesCarp River
Location4.6 MI N of M-123
RouteInterstate 75
CountyMackinac County
StateMichigan
Coordinates46.02362, -84.71154
Functional classRural 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
Deck7 GoodSome minor problems.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Channel and channel protection7 GoodSome minor problems.
Last inspectionDecember 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy7: Better than present minimum criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating76.8 US tons
Inventory rating46.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length303 ft (92.3 m)
Longest span68 ft (20.7 m)
Deck width43 ft (13.1 m)
Roadway width39 ft (12 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,039 (2007)
Projected traffic5,205 by 2018
Trucks9%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesWaterway
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 proposedDeck replacement with only incidental widening
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was I-75 NB over Carp River built?

It was built in 1964, making it 61 years old in 2025.

What condition is I-75 NB over Carp River 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-75 NB over Carp River carry?

About 2,039 vehicles per day (2007 count), of which roughly 9% are trucks.

How long is I-75 NB over Carp River?

The structure is 303 ft (92.3 m) long with a longest span of 68 ft (20.7 m) and a deck 43 ft wide.

Who owns I-75 NB over Carp River?

It is owned by the State Highway Agency.