US Bridges

Dunbarton Road over Black Brook

Good

Hillsborough County, New Hampshire · 0.2 MI Goffstown Tl · Structure no. 016100740004100

Built
1989
36 years old
Condition
Good
inspected July 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
40 ft
1 main span
Daily traffic
3,159
2023 count
Owner
City
City or Municipal Highway Agency

About this bridge

Dunbarton Road over Black Brook is a steel stringer/multi-beam or girder carrying Dunbarton Road over Black Brook in Hillsborough County, New Hampshire. It was built in 1989, so it is 36 years old, younger than the New Hampshire average of 56.9 years.

The most recent inspection reported to the Federal Highway Administration rates it in good condition with a lowest component rating of 7 out of 9. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

It carries about 3,159 vehicles a day, roughly 10% of them trucks, projected to reach 4,675 by 2043. The structure is 40 ft (12.2 m) long and 33 ft wide. If it were closed, the detour would be 1.2 mi (2 km).

Location

Open in Google Maps
CarriesDunbarton Road
CrossesBlack Brook
Location0.2 MI Goffstown Tl
RouteCity Street 0
CountyHillsborough County
StateNew Hampshire
Coordinates43.02532, -71.50466
Functional classUrban Collector

Condition and inspection

Good

All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted.

ComponentRatingMeaning
Deck7 GoodSome minor problems.
Superstructure7 GoodSome minor problems.
Substructure7 GoodSome minor problems.
Channel and channel protection8 Very GoodNo problems noted.
Last inspectionJuly 2024
Inspection intervalevery 24 months
Operating statusOpen, no restriction
ScourFoundations stable; scour above top of footing
Structural evaluation7: Better than present minimum criteria
Deck geometry4: Meets minimum tolerable limits to be left in place as is
Waterway adequacy8: Equal to present desirable criteria
Approach roadway alignment8: Equal to present desirable criteria
Operating rating80.6 US tons
Inventory rating48.4 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1
Design loadHS 25 or greater
Structure length40 ft (12.2 m)
Longest span32 ft (9.8 m)
Deck width33 ft (10.1 m)
Roadway width29 ft (8.8 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic3,159 (2023)
Projected traffic4,675 by 2043
Trucks10%
Lanes on structure2
Traffic directionTwo-way traffic
CarriesHighway
CrossesWaterway
Detour if closed1.2 mi (2 km)
TollOn a free road
National Highway SystemNo

Ownership and planned work

OwnerCity or Municipal Highway Agency
Maintained byCity or Municipal Highway Agency
Historic statusNot eligible for the National Register of Historic Places
Work proposedReplacement because of substandard load-carrying capacity or roadway geometry
Estimated improvement cost$314,000 (2025 estimate)
NavigationNo navigation control on waterway

Frequently asked questions

When was Dunbarton Road over Black Brook built?

It was built in 1989, making it 36 years old in 2025.

What condition is Dunbarton Road over Black Brook in?

The National Bridge Inventory rates it in good condition. All primary components (deck, superstructure, substructure, or culvert) are rated 7 or higher. No significant problems were noted. The last reported inspection was in July 2024.

How much traffic does Dunbarton Road over Black Brook carry?

About 3,159 vehicles per day (2023 count), of which roughly 10% are trucks.

How long is Dunbarton Road over Black Brook?

The structure is 40 ft (12.2 m) long with a longest span of 32 ft (9.8 m) and a deck 33 ft wide.

Who owns Dunbarton Road over Black Brook?

It is owned by the City or Municipal Highway Agency.