US Bridges

M-71 over Shiawassee River

Fair

Shiawassee County, Michigan · 2.3 MI NW of M-78 · Structure no. 000000000009768

Built
1931
94 years old, rebuilt 1999
Condition
Fair
inspected August 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
111 ft
2 main spans
Daily traffic
6,379
2007 count
Owner
State
State Highway Agency

About this bridge

M-71 over Shiawassee River is a steel continuous stringer/multi-beam or girder carrying M-71 over Shiawassee River in Shiawassee County, Michigan. It was built in 1931 and reconstructed in 1999, so it is 94 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 6,379 vehicles a day, roughly 6% of them trucks, projected to reach 7,118 by 2018. The structure is 111 ft (33.8 m) long and 47 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

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CarriesM-71
CrossesShiawassee River
Location2.3 MI NW of M-78
RouteState Highway 71
CountyShiawassee County
StateMichigan
Coordinates42.9461, -84.03602
Functional classRural Minor Arterial

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourUnknown foundation; not evaluated for scour
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating99.6 US tons
Inventory rating59.6 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 25 or greater
Structure length111 ft (33.8 m)
Longest span55 ft (16.7 m)
Deck width47 ft (14.2 m)
Roadway width43 ft (13.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic6,379 (2007)
Projected traffic7,118 by 2018
Trucks6%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 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—
NavigationNo navigation control on waterway

Frequently asked questions

When was M-71 over Shiawassee River built?

It was built in 1931, making it 94 years old in 2025. It was reconstructed in 1999.

What condition is M-71 over Shiawassee 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 August 2023.

How much traffic does M-71 over Shiawassee River carry?

About 6,379 vehicles per day (2007 count), of which roughly 6% are trucks.

How long is M-71 over Shiawassee River?

The structure is 111 ft (33.8 m) long with a longest span of 55 ft (16.7 m) and a deck 47 ft wide.

Who owns M-71 over Shiawassee River?

It is owned by the State Highway Agency.