US Bridges

Main St. (cr 531) over Mill Brook

Fair

Middlesex County, New Jersey · 0.35 Mile North of CR 514 · Structure no. 121B107

Built
1955
70 years old
Condition
Fair
inspected March 2023
Type
Slab
Concrete
Length
20 ft
1 main span
Daily traffic
15,793
2023 count
Owner
County
County Highway Agency

About this bridge

Main St. (cr 531) over Mill Brook is a concrete slab carrying Main St. (cr 531) over Mill Brook in Middlesex County, New Jersey. It was built in 1955, so it is 70 years old, older than the New Jersey average of 58.5 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 15,793 vehicles a day, roughly 4% of them trucks, projected to reach 19,270 by 2043. The structure is 20 ft (6.1 m) long and 62 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesMain St. (cr 531)
CrossesMill Brook
Location0.35 Mile North of CR 514
RouteCounty Highway 531
CountyMiddlesex County
StateNew Jersey
Coordinates40.52062, -74.3572
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.
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy5: Somewhat better than minimum adequacy to tolerate being left in place as is
Approach roadway alignment7: Better than present minimum criteria
Operating rating50 US tons
Inventory rating30 US tons

Structure

Structure typeSlab
MaterialConcrete
DeckConcrete, cast-in-place
Main spans1
Design loadHS 20
Structure length20 ft (6.1 m)
Longest span20 ft (6.1 m)
Deck width62 ft (18.8 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic15,793 (2023)
Projected traffic19,270 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway and pedestrian
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCounty Highway Agency
Maintained byCounty Highway Agency
Historic statusHistorical significance not determinable at this time
Work proposedNone recorded
Estimated improvement cost—
NavigationNo navigation control on waterway

Frequently asked questions

When was Main St. (cr 531) over Mill Brook built?

It was built in 1955, making it 70 years old in 2025.

What condition is Main St. (cr 531) over Mill Brook 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 March 2023.

How much traffic does Main St. (cr 531) over Mill Brook carry?

About 15,793 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Main St. (cr 531) over Mill Brook?

The structure is 20 ft (6.1 m) long with a longest span of 20 ft (6.1 m) and a deck 62 ft wide.

Who owns Main St. (cr 531) over Mill Brook?

It is owned by the County Highway Agency.