Fun fact: Covered bridges were roofed to protect the wood, not the travelers.
Fun fact: Covered bridges were roofed to protect the wood, not the travelers.
Why do engineers love bridges? They're outstanding in their field.
over ST213 WB
2.3 MI N MERRIMAC RIVER
Parametric wireframe generated from real NBI dimensions. Drag to rotate, scroll to zoom.
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This bridge has a Fair overall condition rating of 5 out of 9. While it is not classified as structurally deficient, it shows some deterioration that is being monitored.
The bridge carries 186,800 vehicles per day and is 67 years old (reconstructed in 1974).
Its sufficiency rating of 63.2 places it below the national average of 63.6.
The NBI records a navigation clearance of 14 feet — the minimum vertical space below the bridge deck. The total height of the bridge structure (including towers, railings, and superstructure) may be higher.
For travelers with bridge anxiety
This bridge may cause some awareness for travelers with bridge anxiety, but has manageable characteristics.
This bridge is 131 feet long — a quick crossing, under 5 seconds at highway speed.
A standard overpass design with solid barriers on each side.
About 14 feet above ground — standard overpass height.
About 186,800 vehicles cross daily — very heavy traffic, high congestion risk.
The deck is 140 feet wide with multiple lanes — easy to stay in a center lane.
This bridge crosses over land, not water — no water views below.
This comfort score is designed to help individuals with bridge anxiety plan their travel. All bridges in the National Bridge Inventory are regularly inspected and deemed safe for travel. This is not medical advice — if you experience severe anxiety, please consult a healthcare professional.
Year Built
1959
67 years old (rebuilt 1974)
Structure Type
Prestressed Concrete Stringer/Multi-beam/Girder
Total Length
131 ft
39.9 m
Deck Width
140 ft
42.7 m
Spans
3
sections between supports
Max Span
49 ft
longest unsupported section (14.9 m)
Traffic Lanes
7 lanes
Two-way traffic
Clearance Below
14 ft
navigation clearance under deck
Clearance height compared to familiar objects
Height shown is the navigation clearance below the bridge deck. The total height of the bridge structure (including towers and superstructure) may be higher.
Daily Traffic
186,800vehicles/day
42.73513°N, 71.20361°W
Prestressed Concrete Stringer/Multi-beam/Girder
A prestressed concrete stringer bridge uses pretensioned concrete beams, where steel tendons are stretched before concrete is poured. This creates stronger, lighter spans.
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Data from the National Bridge Inventory (NBI), maintained by the Federal Highway Administration (FHWA).
Data year: 2025. Conditions may have changed since the last inspection.
This information is provided for educational and informational purposes only. It should not be used as the sole basis for any decisions related to bridge safety or transportation planning. Always consult official sources and local authorities for the most current data.