US Bridges

M-46 over Cass River

Fair

Tuscola County, Michigan · 5.5 MI W of M-24 · Structure no. 000000000010413

Built
1934
91 years old, rebuilt 1979
Condition
Fair
inspected September 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
165 ft
3 main spans
Daily traffic
5,255
2007 count
Owner
State
State Highway Agency

About this bridge

M-46 over Cass River is a steel stringer/multi-beam or girder carrying M-46 over Cass River in Tuscola County, Michigan. It was built in 1934 and reconstructed in 1979, so it is 91 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 5,255 vehicles a day, roughly 10% of them trucks, projected to reach 7,000 by 2028. The structure is 165 ft (50.3 m) long and 48 ft wide. If it were closed, the detour would be 3.7 mi (6 km).

Location

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CarriesM-46
CrossesCass River
Location5.5 MI W of M-24
RouteState Highway 46
CountyTuscola County
StateMichigan
Coordinates43.40879, -83.49127
Functional classRural Principal Arterial - Other

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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionSeptember 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry6: Equal to present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment6: Equal to present minimum criteria
Operating rating82.9 US tons
Inventory rating49.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans3
Design loadHS 20
Structure length165 ft (50.3 m)
Longest span55 ft (16.8 m)
Deck width48 ft (14.6 m)
Roadway width44 ft (13.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic5,255 (2007)
Projected traffic7,000 by 2028
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed3.7 mi (6 km)
TollOn a free road
National Highway SystemYes

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 M-46 over Cass River built?

It was built in 1934, making it 91 years old in 2025. It was reconstructed in 1979.

What condition is M-46 over Cass 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 September 2023.

How much traffic does M-46 over Cass River carry?

About 5,255 vehicles per day (2007 count), of which roughly 10% are trucks.

How long is M-46 over Cass River?

The structure is 165 ft (50.3 m) long with a longest span of 55 ft (16.8 m) and a deck 48 ft wide.

Who owns M-46 over Cass River?

It is owned by the State Highway Agency.