US Bridges

Thornton Road over I 8

Fair

Pinal County, Arizona · 5.8 MI W JCT I10 · Structure no. 01196

Built
1967
58 years old
Condition
Fair
inspected October 2023
Type
Stringer/Multi-beam or Girder
Steel Continuous
Length
262 ft
4 main spans
Daily traffic
3,076
2022 count
Owner
State
State Highway Agency

About this bridge

Thornton Road over I 8 is a steel continuous stringer/multi-beam or girder carrying Thornton Road over I 8 in Pinal County, Arizona. It was built in 1967, so it is 58 years old, older than the Arizona average of 47.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in fair condition with a lowest component rating of 5 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 3,076 vehicles a day, roughly 35% of them trucks, projected to reach 3,086 by 2042. The structure is 262 ft (79.9 m) long and 41 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesThornton Road
CrossesI 8
Location5.8 MI W JCT I10
RouteCounty Highway 0
CountyPinal County
StateArizona
Coordinates32.8277, -111.7743
Functional classRural Minor 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.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionOctober 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 geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment8: Equal to present desirable criteria
Operating rating64 US tons
Inventory rating38 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel Continuous
DeckConcrete, cast-in-place
Main spans4
Design loadHS 20
Structure length262 ft (79.9 m)
Longest span81 ft (24.7 m)
Deck width41 ft (12.6 m)
Roadway width38 ft (11.6 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,076 (2022)
Projected traffic3,086 by 2042
Trucks35%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesHighway
Detour if closed1.9 mi (3 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 Thornton Road over I 8 built?

It was built in 1967, making it 58 years old in 2025.

What condition is Thornton Road over I 8 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 October 2023.

How much traffic does Thornton Road over I 8 carry?

About 3,076 vehicles per day (2022 count), of which roughly 35% are trucks.

How long is Thornton Road over I 8?

The structure is 262 ft (79.9 m) long with a longest span of 81 ft (24.7 m) and a deck 41 ft wide.

Who owns Thornton Road over I 8?

It is owned by the State Highway Agency.