Truss bridges are classified as one of three types: through, pony, or deck trusses. On through and pony trusses, the roadway is carried by the lower chords. A through truss has top lateral bracing joining the upper chords; a pony truss does not. A deck truss carries the road on the upper chords.

       Truss bridge designs are named for the arrangements of the triangles that compose the trusses and for the shape of the top chords. The following truss bridge types are found in Mercer County:
 

Diagrams taken from the T.A. Comp and D. Jackson 1977 leaflet Bridge Truss Types: A Guide to Dating and Identifying.