US Bridges

Nj 31 over Willoughby Brook

Fair

Hunterdon County, New Jersey · 0.99 MI North of CR 513 · Structure no. 1013152

Built
1930
95 years old
Condition
Fair
inspected March 2023
Type
Arch - Deck
Concrete
Length
29 ft
1 main span
Daily traffic
24,297
2023 count
Owner
State
State Highway Agency

About this bridge

Nj 31 over Willoughby Brook is a concrete arch - deck carrying Nj 31 over Willoughby Brook in Hunterdon County, New Jersey. It was built in 1930, so it is 95 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 24,297 vehicles a day, roughly 4% of them trucks, projected to reach 29,647 by 2043. The structure is 29 ft (8.8 m) long and 44 ft wide. If it were closed, the detour would be 1.9 mi (3 km).

Location

Open in Google Maps
CarriesNj 31
CrossesWilloughby Brook
Location0.99 MI North of CR 513
RouteState Highway 31
CountyHunterdon County
StateNew Jersey
Coordinates40.67162, -74.91513
Functional classUrban Other Principal 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
Superstructure6 SatisfactoryStructural elements show some minor deterioration.
Substructure6 SatisfactoryStructural elements show some minor deterioration.
Channel and channel protection6 SatisfactoryStructural elements show some minor deterioration.
Last inspectionMarch 2023
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourScour critical; foundations unstable for calculated scour conditions
Structural evaluation6: Equal to present minimum criteria
Deck geometry5: Somewhat better than minimum adequacy to tolerate being left in place as is
Waterway adequacy6: Equal to present minimum criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating110.1 US tons
Inventory rating110.1 US tons

Structure

Structure typeArch - Deck
MaterialConcrete
DeckNot applicable
Main spans1
Design loadUnknown
Structure length29 ft (8.8 m)
Longest span29 ft (8.8 m)
Deck width44 ft (13.4 m)
Roadway width40 ft (12.2 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic24,297 (2023)
Projected traffic29,647 by 2043
Trucks4%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.9 mi (3 km)
TollOn a free road
National Highway SystemYes

Ownership and planned work

OwnerState Highway Agency
Maintained byState Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedOther structural work, including hydraulic replacements
Estimated improvement cost$158,000 (2023 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Nj 31 over Willoughby Brook built?

It was built in 1930, making it 95 years old in 2025.

What condition is Nj 31 over Willoughby 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 Nj 31 over Willoughby Brook carry?

About 24,297 vehicles per day (2023 count), of which roughly 4% are trucks.

How long is Nj 31 over Willoughby Brook?

The structure is 29 ft (8.8 m) long with a longest span of 29 ft (8.8 m) and a deck 44 ft wide.

Who owns Nj 31 over Willoughby Brook?

It is owned by the State Highway Agency.