US Bridges

I-75 NB over Au Sable River

Fair

Crawford County, Michigan · 0.7 MI N of M-72 · Structure no. 000000000002039

Built
1960
65 years old
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
64 ft
1 main span
Daily traffic
8,126
2022 count
Owner
State
State Highway Agency

About this bridge

I-75 NB over Au Sable River is a steel stringer/multi-beam or girder carrying I-75 NB over Au Sable River in Crawford County, Michigan. It was built in 1960, so it is 65 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 5 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 8,126 vehicles a day, roughly 11% of them trucks. The structure is 64 ft (19.5 m) long and 47 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesI-75 NB
CrossesAu Sable River
Location0.7 MI N of M-72
RouteInterstate 75
CountyCrawford County
StateMichigan
Coordinates44.66637, -84.69648
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry8: Equal to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating87.9 US tons
Inventory rating52.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20 + Mod
Structure length64 ft (19.5 m)
Longest span63 ft (19.1 m)
Deck width47 ft (14.4 m)
Roadway width42 ft (12.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic8,126 (2022)
Projected traffic—
Trucks11%
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 proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was I-75 NB over Au Sable River built?

It was built in 1960, making it 65 years old in 2025.

What condition is I-75 NB over Au Sable 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 May 2024.

How much traffic does I-75 NB over Au Sable River carry?

About 8,126 vehicles per day (2022 count), of which roughly 11% are trucks.

How long is I-75 NB over Au Sable River?

The structure is 64 ft (19.5 m) long with a longest span of 63 ft (19.1 m) and a deck 47 ft wide.

Who owns I-75 NB over Au Sable River?

It is owned by the State Highway Agency.