US Bridges

M-123 over I-75 NB

Poor

Mackinac County, Michigan · @ M-123 · Structure no. 000000000005953

Built
1963
62 years old
Condition
Poor
inspected April 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
196 ft
4 main spans
Daily traffic
1,808
2007 count
Owner
State
State Highway Agency

About this bridge

M-123 over I-75 NB is a steel stringer/multi-beam or girder carrying M-123 over I-75 NB in Mackinac County, Michigan. It was built in 1963, so it is 62 years old, older than the Michigan average of 48.3 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 1,808 vehicles a day, roughly 5% of them trucks, projected to reach 2,088 by 2018. The structure is 196 ft (59.7 m) long and 37 ft wide.

Location

Open in Google Maps
CarriesM-123
CrossesI-75 NB
Location@ M-123
RouteState Highway 123
CountyMackinac County
StateMichigan
Coordinates45.96438, -84.75186
Functional classRural Minor Arterial

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck4 PoorAdvanced section loss, deterioration, spalling or scour.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Last inspectionApril 2024
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry5: Somewhat better than minimum adequacy to tolerate being 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 loadHS 20
Structure length196 ft (59.7 m)
Longest span61 ft (18.6 m)
Deck width37 ft (11.2 m)
Roadway width33 ft (10 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic1,808 (2007)
Projected traffic2,088 by 2018
Trucks5%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
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 proposedDeck replacement with only incidental widening
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was M-123 over I-75 NB built?

It was built in 1963, making it 62 years old in 2025.

What condition is M-123 over I-75 NB in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in April 2024.

How much traffic does M-123 over I-75 NB carry?

About 1,808 vehicles per day (2007 count), of which roughly 5% are trucks.

How long is M-123 over I-75 NB?

The structure is 196 ft (59.7 m) long with a longest span of 61 ft (18.6 m) and a deck 37 ft wide.

Who owns M-123 over I-75 NB?

It is owned by the State Highway Agency.