US Bridges

I 15 over Frontage Road

Fair

Clark County, Idaho · 2.0 S. Spencer · Structure no. 000000000011940

Built
1965
60 years old, rebuilt 1990
Condition
Fair
inspected June 2023
Type
Frame
Concrete
Length
28 ft
1 main span
Daily traffic
3,700
2023 count
Owner
State
State Highway Agency

About this bridge

I 15 over Frontage Road is a concrete frame carrying I 15 over Frontage Road in Clark County, Idaho. It was built in 1965 and reconstructed in 1990, so it is 60 years old, older than the Idaho average of 45.3 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 3,700 vehicles a day, roughly 68% of them trucks, projected to reach 5,550 by 2042. The structure is 28 ft (8.5 m) long and 178 ft wide. If it were closed, the detour would be 49.7 mi (80 km).

Location

Open in Google Maps
CarriesI 15
CrossesFrontage Road
Location2.0 S. Spencer
RouteInterstate 15
CountyClark County
StateIdaho
Coordinates44.33275, -112.17428
Functional classRural Principal Arterial - Interstate

Condition and inspection

Fair

The lowest-rated primary component is rated 5 or 6. Minor deterioration is present but the structure is sound.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJune 2023
Inspection intervalevery 48 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 rating80 US tons
Inventory rating48 US tons

Structure

Structure typeFrame
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length28 ft (8.5 m)
Longest span28 ft (8.5 m)
Deck width178 ft (54.3 m)
Roadway width176 ft (53.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,700 (2023)
Projected traffic5,550 by 2042
Trucks68%
Lanes on structure4
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed49.7 mi (80 km)
TollOn a free road
National Highway SystemYes
Strategic Highway NetworkInterstate STRAHNET route

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNot applicable (no waterway)

Frequently asked questions

When was I 15 over Frontage Road built?

It was built in 1965, making it 60 years old in 2025. It was reconstructed in 1990.

What condition is I 15 over Frontage Road 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 June 2023.

How much traffic does I 15 over Frontage Road carry?

About 3,700 vehicles per day (2023 count), of which roughly 68% are trucks.

How long is I 15 over Frontage Road?

The structure is 28 ft (8.5 m) long with a longest span of 28 ft (8.5 m) and a deck 178 ft wide.

Who owns I 15 over Frontage Road?

It is owned by the State Highway Agency.