US Bridges

ST121 West ST over I 495

Fair

Norfolk County, Massachusetts · .7 MI NW of ST 1A · Structure no. W460083VLDOTNBI

Built
1966
59 years old
Condition
Fair
inspected July 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
247 ft
2 main spans
Daily traffic
10,733
2024 count
Owner
State
State Highway Agency

About this bridge

ST121 West ST over I 495 is a steel stringer/multi-beam or girder carrying ST121 West ST over I 495 in Norfolk County, Massachusetts. It was built in 1966, so it is 59 years old, younger than the Massachusetts average of 63.8 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 10,733 vehicles a day, roughly 10% of them trucks, projected to reach 16,267 by 2031. The structure is 247 ft (75.3 m) long and 54 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesST121 West ST
CrossesI 495
Location.7 MI NW of ST 1A
RouteState Highway 121
CountyNorfolk County
StateMassachusetts
Coordinates42.04391, -71.35714
Functional classUrban 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 inspectionJuly 2024
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 rating55.9 US tons
Inventory rating24.5 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans2
Design loadH 20
Structure length247 ft (75.3 m)
Longest span122 ft (37.2 m)
Deck width54 ft (16.5 m)
Roadway width44 ft (13.4 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic10,733 (2024)
Projected traffic16,267 by 2031
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
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 proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$12.2 million (2025 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was ST121 West ST over I 495 built?

It was built in 1966, making it 59 years old in 2025.

What condition is ST121 West ST over I 495 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 July 2024.

How much traffic does ST121 West ST over I 495 carry?

About 10,733 vehicles per day (2024 count), of which roughly 10% are trucks.

How long is ST121 West ST over I 495?

The structure is 247 ft (75.3 m) long with a longest span of 122 ft (37.2 m) and a deck 54 ft wide.

Who owns ST121 West ST over I 495?

It is owned by the State Highway Agency.