Structure B166618R0DOTNBI · Suffolk County, MA
Carries I 93 NB over HWY W Fourth ST, B16661b Unit 1.
619 ft end to end, longest span 150 ft: about 1.7 football fields. Lengths and the semi-truck on the deck are drawn to the same scale. Each part is colored by its latest inspection rating. The inventory records lengths but not heights or the layout of the shorter spans, so those are drawn as typical for a segmental box-girder bridge.
| State | Massachusetts |
| County | Suffolk |
| Location | B16661b Unit 1 |
| Carries | I 93 NB |
| Crosses | HWY W Fourth ST |
| Coordinates | 42.34284, -71.06179 |
| Material | Prestressed Concrete Continuous |
| Design | Segmental Box Girder |
| Total Length | 618.8 ft (188.6 m) |
| Max Span | 149.9 ft (45.7 m) |
| Deck Width | 54.1 ft (16.5 m) |
| Deck Area | 3111.9 sq m |
| Main Spans | 5 |
| Year Built | 2002 |
| Avg Daily Traffic | 82,300 (2019) |
| Lanes On Bridge | 3 |
| Lanes Under Bridge | 3 |
| Last Inspection | March 2022 |
| Inspection Frequency | Every 24 months |
| Owner | State Highway Agency |
| Historical Significance | Historical significance is not determined |
| Scour Critical | Not applicable |
| Structure Number | B166618R0DOTNBI |
Inspectors rate each major part of a bridge (the deck you drive on, the superstructure of beams that holds it up, and the substructure of piers and abutments beneath) on a 0–9 scale. A bridge's overall condition is its lowest of those ratings, so one deteriorated component makes the whole bridge "poor."
A poor rating is not a closure. It means the bridge is flagged for priority repair or replacement; bridges judged unsafe are closed or posted with weight limits. The waterway (channel) rating is reported, but it does not count toward the overall classification.