US Bridges

ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx

Fair

Middlesex County, Massachusetts · 30 M S of JCT SR16&SR99 · Structure no. E120013GHDOT634

Built
1954
71 years old
Condition
Fair
inspected August 2024
Type
Stringer/Multi-beam or Girder
Steel
Length
129 ft
1 main span
Daily traffic
42,000
2024 count
Owner
State
State Highway Agency

About this bridge

ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx is a steel stringer/multi-beam or girder carrying ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx in Middlesex County, Massachusetts. It was built in 1954, so it is 71 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 42,000 vehicles a day, roughly 12% of them trucks, projected to reach 50,538 by 2031. The structure is 129 ft (39.3 m) long and 51 ft wide. If it were closed, the detour would be 0.6 mi (1 km).

Location

Open in Google Maps
CarriesST 99 Sb/Main ST
CrossesRR Mbta/Bmrr/Csx
Location30 M S of JCT SR16&SR99
RouteState Highway 99
CountyMiddlesex County
StateMassachusetts
Coordinates42.40159, -71.06096
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
Deck5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Superstructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Substructure5 FairAll primary structural elements are sound but may have minor section loss, cracking, spalling or scour.
Last inspectionAugust 2024
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 alignment8: Equal to present desirable criteria
Operating rating49.9 US tons
Inventory rating32.3 US tons

Structure

Structure typeStringer/Multi-beam or Girder
MaterialSteel
DeckConcrete, cast-in-place
Main spans1 (+2 approach)
Design loadHS 20
Structure length129 ft (39.3 m)
Longest span85 ft (25.9 m)
Deck width51 ft (15.5 m)
Roadway width36 ft (11 m)
Vertical clearance over deckUnrestricted

Traffic and service

Average daily traffic42,000 (2024)
Projected traffic50,538 by 2031
Trucks12%
Lanes on structure3
Traffic directionOne-way traffic
CarriesHighway and pedestrian
CrossesRailroad
Detour if closed0.6 mi (1 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 proposedRehabilitation because of general structure deterioration or inadequate strength
Estimated improvement cost$6 million (2025 estimate)
NavigationNot applicable (no waterway)

Frequently asked questions

When was ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx built?

It was built in 1954, making it 71 years old in 2025.

What condition is ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx 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 August 2024.

How much traffic does ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx carry?

About 42,000 vehicles per day (2024 count), of which roughly 12% are trucks.

How long is ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx?

The structure is 129 ft (39.3 m) long with a longest span of 85 ft (25.9 m) and a deck 51 ft wide.

Who owns ST 99 Sb/Main ST over RR Mbta/Bmrr/Csx?

It is owned by the State Highway Agency.