Bridge Type Encyclopedia
From ancient stone arches to modern cable-stayed marvels, explore every type of bridge found in the United States. Learn how each design works, its strengths and weaknesses, and browse real examples from the National Bridge Inventory.
Bridge Types
12
Total US Bridges
624,191
Beam/Girder Bridge
241,624 bridges (38.7%)
The most common bridge type in America, using horizontal beams supported by piers to carry the deck.
Culvert
148,526 bridges (23.8%)
Enclosed conduits under roads that carry water or provide passage, often overlooked but incredibly numerous.
Slab Bridge
82,465 bridges (13.2%)
The simplest bridge form: a flat concrete slab spanning between supports, common for short crossings.
Box Beam Bridge
70,776 bridges (11.3%)
Bridges using hollow rectangular or trapezoidal sections that provide excellent strength and torsional resistance.
Truss Bridge
7,293 bridges (1.2%)
Bridges built from interconnected triangular elements, combining strength and material efficiency.
Arch Bridge
6,854 bridges (1.1%)
One of the oldest bridge forms, using a curved structure to transfer loads outward to abutments at each end.
Movable Bridge
798 bridges (0.1%)
Bridges that open or move to allow ships to pass, including lift, bascule, and swing types.
Segmental Bridge
421 bridges (0.1%)
Modern concrete bridges built from precast segments joined by post-tensioning, enabling rapid construction of long spans.
Suspension Bridge
96 bridges (0.0%)
Iconic bridges with a deck hung from cables draped over tall towers, capable of spanning enormous distances.
Cable-Stayed Bridge
70 bridges (0.0%)
Modern bridges where cables run directly from towers to the deck, creating a dramatic fan or harp pattern.
Cantilever Bridge
Bridges built outward from piers using balanced projecting arms, ideal for spanning wide obstacles without falsework.
Covered Bridge
Historic timber bridges enclosed by a roof and siding, protecting the wooden structure from the elements.
How Are Bridges Classified?
Bridges are classified by their primary structural system, which determines how they transfer loads from the deck to the foundations. The Federal Highway Administration's National Bridge Inventory (NBI) uses numeric design type codes to categorize each of the more than 600,000 bridges in the United States.
The most common classification factors are the main spanning material (steel, concrete, wood, or stone) and the structural system (beam, truss, arch, suspension, cable-stayed, etc.). A bridge's type determines its ideal span range, load capacity, construction method, maintenance needs, and visual character.
Each type has evolved to solve specific engineering challenges. Simple beam bridges are economical for short spans. Arches and trusses extend the range to medium spans. Cable-stayed and suspension bridges reach the longest distances. Understanding bridge types helps engineers choose the right design for each crossing and helps the public appreciate the infrastructure they depend on every day.