Included in this study are most of the convict built structures that were used for bridges, including: * Stone Arch Bridges * Brick Bridges up until 1880 if they had not been greatly modified * Metal Bridges up until 1880 * Concrete Bridges up until 1910 * Bridges that have historic or constructional significance * Bridges found in the 2004 Landmark Bridges stamp series. No wooden bridges are included. Most of the above bridge types are covered, but there are some exceptions.
