US Bridges

M-56 over I-80

Good

Cass County, Iowa · At Jct. SR M-56 · Structure no. 000000000017970

Built
1965
60 years old, rebuilt 2014
Condition
Good
inspected March 2023
Type
Stringer/Multi-beam or Girder
Prestressed Concrete
Length
227 ft
4 main spans
Daily traffic
159
2022 count
Owner
State
State Highway Agency

About this bridge

M-56 over I-80 is a prestressed concrete stringer/multi-beam or girder carrying M-56 over I-80 in Cass County, Iowa. It was built in 1965 and reconstructed in 2014, so it is 60 years old, older than the Iowa average of 45.5 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 159 vehicles a day, roughly 7% of them trucks, projected to reach 159 by 2042. The structure is 227 ft (69.2 m) long and 32 ft wide. If it were closed, the detour would be 6.8 mi (11 km).

Location

Open in Google Maps
CarriesM-56
CrossesI-80
LocationAt Jct. SR M-56
RouteCounty Highway 0
CountyCass County
StateIowa
Coordinates41.49683, -95.11801
Functional classRural Major Collector

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck8 Very GoodNo problems noted.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation5: Somewhat better than minimum adequacy to tolerate being left in place as is
Deck geometry6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating71 US tons
Inventory rating20.2 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialPrestressed Concrete
DeckConcrete, cast-in-place
Main spans4
Design loadH 20
Structure length227 ft (69.2 m)
Longest span69 ft (21 m)
Deck width32 ft (9.9 m)
Roadway width30 ft (9.1 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic159 (2022)
Projected traffic159 by 2042
Trucks7%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesOverpass structure at an interchange
CrossesHighway
Detour if closed6.8 mi (11 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—
NavigationNot applicable (no waterway)

Frequently asked questions

When was M-56 over I-80 built?

It was built in 1965, making it 60 years old in 2025. It was reconstructed in 2014.

What condition is M-56 over I-80 in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in March 2023.

How much traffic does M-56 over I-80 carry?

About 159 vehicles per day (2022 count), of which roughly 7% are trucks.

How long is M-56 over I-80?

The structure is 227 ft (69.2 m) long with a longest span of 69 ft (21 m) and a deck 32 ft wide.

Who owns M-56 over I-80?

It is owned by the State Highway Agency.