US Bridges

M-71 over Shiawassee River

Fair

Shiawassee County, Michigan · In Owosso · Structure no. 000000000009767

Built
1983
42 years old
Condition
Fair
inspected August 2023
Type
Stringer/Multi-beam or Girder
Steel
Length
120 ft
2 main spans
Daily traffic
8,752
2007 count
Owner
State
State Highway Agency

About this bridge

M-71 over Shiawassee River is a steel stringer/multi-beam or girder carrying M-71 over Shiawassee River in Shiawassee County, Michigan. It was built in 1983, so it is 42 years old, younger 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 8,752 vehicles a day, roughly 4% of them trucks, projected to reach 11,104 by 2018. The structure is 120 ft (36.5 m) long and 82 ft wide.

Location

Open in Google Maps
CarriesM-71
CrossesShiawassee River
LocationIn Owosso
RouteState Highway 71
CountyShiawassee County
StateMichigan
Coordinates42.99468, -84.17069
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Channel and channel protection7 GoodSome minor problems.
Last inspectionAugust 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry7: Better than present minimum criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating66.8 US tons
Inventory rating40 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20
Structure length120 ft (36.5 m)
Longest span60 ft (18.2 m)
Deck width82 ft (25.1 m)
Roadway width64 ft (19.5 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic8,752 (2007)
Projected traffic11,104 by 2018
Trucks4%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed—
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 1983, making it 42 years old in 2025.

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 8,752 vehicles per day (2007 count), of which roughly 4% are trucks.

How long is M-71 over Shiawassee River?

The structure is 120 ft (36.5 m) long with a longest span of 60 ft (18.2 m) and a deck 82 ft wide.

Who owns M-71 over Shiawassee River?

It is owned by the State Highway Agency.