Criteria for Preservation and Adaptive Use of Historic Highway Structures

About the report:

Metal truss bridges are uniquely indigenous products of American engineering and construction technology, and in recent years their historic significance has been increasingly recognized along with that of other early engineering structures. Some trusses that warrant inclusion on the National Register of Historic Places require renovation or replacement to meet modern traffic demands. Conflicting requirements of federal preservation and highway safety legislation demand that standards be developed to permit, early in the replacement planning process, objective identification of those trusses that warrant retention because of historic significance. Based upon a statewide survey of metal truss bridges in Virginia, an objective numerical rating system for historic significance has been developed that considers characteristics in three categories: documentation (age and builder), technology, and environmental factors. This system was applied to 58 bridges selected from approximately 500 surveyed statewide. Based upon this study the following conclusions appear warranted. 1. While historic significance is in some measure subjective (no more so than the sufficiency rating), an objective numerical rating system provides a useful tool for identifying bridges of special significance and guiding decisions on preservation or adaptive use. 2. Information in three broad categories - documentation, technological significance, and environmental factors provides necessary characteristics for establishing significance. 3. While developed from data on metal trusses in Virginia, the system is generally applicable to other types of bridges in other areas. 4. While few metal truss bridges of national significance survive in Virginia, there are several examples worthy of preservation and numerous examples reflecting the various technologies of nineteenth century bridge design and construction. 5. Virginia still possesses a sufficient diversity of truss types, materials, and geographical, distribution to serve as a valuable resource for appreciation by lay persons and study by specialists.

Authors