US Bridges

US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr

Fair

Suffolk County, Massachusetts · Big Mystic Upper · Structure no. B160174X4DOTNBI

Built
1950
75 years old
Condition
Fair
inspected November 2023
Type
Truss - Thru
Steel Continuous
Length
1,524 ft
3 main spans
Daily traffic
41,655
2022 count
Owner
State
State Highway Agency

About this bridge

US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr is a steel continuous truss - thru carrying US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr in Suffolk County, Massachusetts. It was built in 1950, so it is 75 years old, older 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 41,655 vehicles a day, roughly 9% of them trucks, projected to reach 45,800 by 2032. The structure is 1,524 ft (464.5 m) long and 42 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

Open in Google Maps
CarriesUS 1 Sb/B Mystc U
CrossesUS 1 Nb/Big Mystic Lowr
LocationBig Mystic Upper
RouteU.S. Route 1
CountySuffolk County
StateMassachusetts
Coordinates42.3851, -71.04729
Functional classUrban Principal Arterial - Other Freeway or Expressway

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.
Channel and channel protection7 GoodSome minor problems.
Last inspectionNovember 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 geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment7: Better than present minimum criteria
Operating rating40.1 US tons
Inventory rating24 US tons

Structure

Structure typeTruss - Thru
MaterialSteel Continuous
DeckClosed grating
Main spans3
Design loadHS 20
Structure length1,524 ft (464.5 m)
Longest span801 ft (244.1 m)
Deck width42 ft (12.7 m)
Roadway width36 ft (11 m)
Vertical clearance over deck16 ft (4.9 m)

Traffic and service

Average daily traffic41,655 (2022)
Projected traffic45,800 by 2032
Trucks9%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway
CrossesHighway
Detour if closed5 mi (8 km)
TollToll bridge
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusPossibly eligible for the National Register; requires further investigation
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$57.5 million (2025 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr built?

It was built in 1950, making it 75 years old in 2025.

What condition is US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr 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 November 2023.

How much traffic does US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr carry?

About 41,655 vehicles per day (2022 count), of which roughly 9% are trucks.

How long is US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr?

The structure is 1,524 ft (464.5 m) long with a longest span of 801 ft (244.1 m) and a deck 42 ft wide.

Who owns US 1 Sb/B Mystc U over US 1 Nb/Big Mystic Lowr?

It is owned by the State Highway Agency.