US Bridges

US-31 NB over Old US-31

Fair

Mason County, Michigan · 3.5 MI SE of Ludington · Structure no. 000000000006652

Built
1986
39 years old
Condition
Fair
inspected April 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
113 ft
1 main span
Daily traffic
4,256
2007 count
Owner
State
State Highway Agency

About this bridge

US-31 NB over Old US-31 is a steel stringer/multi-beam or girder carrying US-31 NB over Old US-31 in Mason County, Michigan. It was built in 1986, so it is 39 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 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 4,256 vehicles a day, roughly 15% of them trucks, projected to reach 3,385 by 2018. The structure is 113 ft (34.4 m) long and 48 ft wide. If it were closed, the detour would be 3.1 mi (5 km).

CarriesUS-31 NB
CrossesOld US-31
Location3.5 MI SE of Ludington
RouteU.S. Route 31
Coordinates43.91518, -86.40311
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure7 GoodSome minor problems.
Last inspectionApril 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry9: Superior to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating81.5 US tons
Inventory rating48.6 US tons

Structure

MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 25 or greater
Structure length113 ft (34.4 m)
Longest span113 ft (34.4 m)
Deck width48 ft (14.6 m)
Roadway width45 ft (13.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic4,256 (2007)
Projected traffic3,385 by 2018
Trucks15%
Lanes on structure2
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed3.1 mi (5 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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was US-31 NB over Old US-31 built?

It was built in 1986, making it 39 years old in 2025.

What condition is US-31 NB over Old US-31 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 April 2024.

How much traffic does US-31 NB over Old US-31 carry?

About 4,256 vehicles per day (2007 count), of which roughly 15% are trucks.

How long is US-31 NB over Old US-31?

The structure is 113 ft (34.4 m) long with a longest span of 113 ft (34.4 m) and a deck 48 ft wide.

Who owns US-31 NB over Old US-31?

It is owned by the State Highway Agency.