US Bridges

US 1 SB over US 1 NB

Poor

Suffolk County, Massachusetts · S Appr Tobin · Structure no. B16409927DOTNBI

Built
1994
31 years old
Condition
Poor
inspected September 2023
Type
Box Beam or Girders - Multiple
Prestressed Concrete Continuous
Length
710 ft
9 main spans
Daily traffic
34,040
2023 count
Owner
State
State Highway Agency

About this bridge

US 1 SB over US 1 NB is a prestressed concrete continuous box beam or girders - multiple carrying US 1 SB over US 1 NB in Suffolk County, Massachusetts. It was built in 1994, so it is 31 years old, younger than the Massachusetts average of 63.8 years.

The most recent inspection reported to the Federal Highway Administration rates it in poor condition with a lowest component rating of 4 out of 9. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

It carries about 34,040 vehicles a day, roughly 11% of them trucks, projected to reach 70,595 by 2032. The structure is 710 ft (216.4 m) long and 43 ft wide. If it were closed, the detour would be 5 mi (8 km).

Location

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CarriesUS 1 SB
CrossesUS 1 NB
LocationS Appr Tobin
RouteU.S. Route 1
CountySuffolk County
StateMassachusetts
Coordinates42.37418, -71.05816
Functional classUrban Principal Arterial - Other Freeway or Expressway

Condition and inspection

Poor

The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions.

ComponentRatingMeaning
Deck6 SatisfactoryStructural elements show some minor deterioration.
Superstructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Substructure4 PoorAdvanced section loss, deterioration, spalling or scour.
Last inspectionSeptember 2023
Inspection intervalevery 12 months
Operating statusOpen, no restriction
ScourBridge not over waterway
Structural evaluation4: Meets minimum tolerable limits to be left in place as is
Deck geometry2: Basically intolerable, requiring high priority of replacement
Approach roadway alignment7: Better than present minimum criteria
Operating rating94.2 US tons
Inventory rating50.6 US tons

Structure

Structure typeBox Beam or Girders - Multiple
MaterialPrestressed Concrete Continuous
DeckConcrete, cast-in-place
Main spans9
Design loadHS 20
Structure length710 ft (216.4 m)
Longest span80 ft (24.4 m)
Deck width43 ft (13.2 m)
Roadway width36 ft (11 m)
Vertical clearance over deck20 ft (6 m)

Traffic and service

Average daily traffic34,040 (2023)
Projected traffic70,595 by 2032
Trucks11%
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 statusHistorical significance not determinable at this time
Work proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$27.9 million (2025 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was US 1 SB over US 1 NB built?

It was built in 1994, making it 31 years old in 2025.

What condition is US 1 SB over US 1 NB in?

The National Bridge Inventory rates it in poor condition. The lowest-rated primary component is rated 4 or below, indicating advanced deterioration. Poor does not mean unsafe; such bridges are inspected more often and may carry load restrictions. The last reported inspection was in September 2023.

How much traffic does US 1 SB over US 1 NB carry?

About 34,040 vehicles per day (2023 count), of which roughly 11% are trucks.

How long is US 1 SB over US 1 NB?

The structure is 710 ft (216.4 m) long with a longest span of 80 ft (24.4 m) and a deck 43 ft wide.

Who owns US 1 SB over US 1 NB?

It is owned by the State Highway Agency.