US Bridges

M-28 over Rock River

Fair

Alger County, Michigan · 5.1 MI NW of Au Train · Structure no. 000000000000046

Built
1932
93 years old, rebuilt 1975
Condition
Fair
inspected May 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
40 ft
1 main span
Daily traffic
3,093
2007 count
Owner
State
State Highway Agency

About this bridge

M-28 over Rock River is a steel stringer/multi-beam or girder carrying M-28 over Rock River in Alger County, Michigan. It was built in 1932 and reconstructed in 1975, so it is 93 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 3,093 vehicles a day, roughly 10% of them trucks, projected to reach 4,926 by 2018. The structure is 40 ft (12.2 m) long and 50 ft wide. If it were closed, the detour would be 39.1 mi (63 km).

Location

Open in Google Maps
CarriesM-28
CrossesRock River
Location5.1 MI NW of Au Train
RouteState Highway 28
CountyAlger County
StateMichigan
Coordinates46.46383, -86.91603
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
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection7 GoodSome minor problems.
Last inspectionMay 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment7: Better than present minimum criteria
Operating rating97.6 US tons
Inventory rating63.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length40 ft (12.2 m)
Longest span38 ft (11.7 m)
Deck width50 ft (15.2 m)
Roadway width47 ft (14.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,093 (2007)
Projected traffic4,926 by 2018
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed39.1 mi (63 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 proposedDeck replacement with only incidental widening
Estimated improvement cost$7,000
NavigationNo navigation control on waterway

Frequently asked questions

When was M-28 over Rock River built?

It was built in 1932, making it 93 years old in 2025. It was reconstructed in 1975.

What condition is M-28 over Rock 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 M-28 over Rock River carry?

About 3,093 vehicles per day (2007 count), of which roughly 10% are trucks.

How long is M-28 over Rock River?

The structure is 40 ft (12.2 m) long with a longest span of 38 ft (11.7 m) and a deck 50 ft wide.

Who owns M-28 over Rock River?

It is owned by the State Highway Agency.