US Bridges

Mackinaw RD over I-75

Fair

Bay County, Michigan · 6.5 MI NW of Bay City · Structure no. 000000000000633

Built
1967
58 years old, rebuilt 2019
Condition
Fair
inspected March 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
253 ft
4 main spans
Daily traffic
2,598
2016 count
Owner
State
State Highway Agency

About this bridge

Mackinaw RD over I-75 is a steel stringer/multi-beam or girder carrying Mackinaw RD over I-75 in Bay County, Michigan. It was built in 1967 and reconstructed in 2019, so it is 58 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 2,598 vehicles a day, roughly 3% of them trucks, projected to reach 2,988 by 2036. The structure is 253 ft (77.1 m) long and 32 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

Open in Google Maps
CarriesMackinaw RD
CrossesI-75
Location6.5 MI NW of Bay City
RouteCounty Highway 0
CountyBay County
StateMichigan
Coordinates43.65138, -83.98995
Functional classRural Minor Collector

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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure8 Very GoodNo problems noted.
Last inspectionMarch 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment7: Better than present minimum criteria
Operating rating84.3 US tons
Inventory rating50.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans4
Design loadH 15
Structure length253 ft (77.1 m)
Longest span91 ft (27.6 m)
Deck width32 ft (9.9 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic2,598 (2016)
Projected traffic2,988 by 2036
Trucks3%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemNo

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 Mackinaw RD over I-75 built?

It was built in 1967, making it 58 years old in 2025. It was reconstructed in 2019.

What condition is Mackinaw RD over I-75 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 March 2024.

How much traffic does Mackinaw RD over I-75 carry?

About 2,598 vehicles per day (2016 count), of which roughly 3% are trucks.

How long is Mackinaw RD over I-75?

The structure is 253 ft (77.1 m) long with a longest span of 91 ft (27.6 m) and a deck 32 ft wide.

Who owns Mackinaw RD over I-75?

It is owned by the State Highway Agency.