US Bridges

SR-18 Intchg X-Rd over I-15 (SR-15) & Int.

Fair

Washington County, Utah · So.St.George Interchange · Structure no. 0C 588

Built
1972
53 years old, rebuilt 1992
Condition
Fair
inspected January 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
283 ft
2 main spans
Daily traffic
33,564
2022 count
Owner
State
State Highway Agency

About this bridge

SR-18 Intchg X-Rd over I-15 (SR-15) & Int. is a steel continuous stringer/multi-beam or girder carrying SR-18 Intchg X-Rd over I-15 (SR-15) & Int. in Washington County, Utah. It was built in 1972 and reconstructed in 1992, so it is 53 years old, older than the Utah average of 40.1 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 33,564 vehicles a day, roughly 35% of them trucks, projected to reach 40,277 by 2042. The structure is 283 ft (86.2 m) long and 104 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

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CarriesSR-18 Intchg X-Rd
CrossesI-15 (SR-15) & Int.
LocationSo.St.George Interchange
RouteState Highway 18
CountyWashington County
StateUtah
Coordinates37.08329, -113.58262
Functional classUrban Other Principal Arterial

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.
Superstructure7 GoodSome minor problems.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionJanuary 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation6: Equal to present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating56.4 US tons
Inventory rating35.1 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans2
Design loadHS 20 + Mod
Structure length283 ft (86.2 m)
Longest span138 ft (42.2 m)
Deck width104 ft (31.8 m)
Roadway width74 ft (22.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic33,564 (2022)
Projected traffic40,277 by 2042
Trucks35%
Lanes on structure6
Traffic directionTwo-way traffic
CarriesOverpass structure at an interchange
CrossesHighway
Detour if closed5 mi (8 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 SR-18 Intchg X-Rd over I-15 (SR-15) & Int. built?

It was built in 1972, making it 53 years old in 2025. It was reconstructed in 1992.

What condition is SR-18 Intchg X-Rd over I-15 (SR-15) & Int. 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 January 2023.

How much traffic does SR-18 Intchg X-Rd over I-15 (SR-15) & Int. carry?

About 33,564 vehicles per day (2022 count), of which roughly 35% are trucks.

How long is SR-18 Intchg X-Rd over I-15 (SR-15) & Int.?

The structure is 283 ft (86.2 m) long with a longest span of 138 ft (42.2 m) and a deck 104 ft wide.

Who owns SR-18 Intchg X-Rd over I-15 (SR-15) & Int.?

It is owned by the State Highway Agency.