The National Academies

NCHRP 25-25/Task 118 [Final]

Context-Sensitive Design Options for Workhorse Bridges in Rural Historic Districts
[ NCHRP 25-25 (Research for the AASHTO Committee on Environment and Sustainability) ]

  Project Data
Funds: $110,000
Research Agency: Louis Berger U.S. Inc.
Principal Investigator: Dr. Steven Bedford & Ms. Camilla Deiber
Effective Date: 11/30/2018
Completion Date: 11/29/2019

STATUS:  Research is complete. Final report available HERE


A workhorse bridge is a bridge less than 300 feet in length (one or two spans), generally from constant girder-type structures assembled from standard structural components and systems.  Such bridges are common in rural areas and the replacement of bridges in rural areas is a common project type for most state departments of transportation (DOTs). When replacing a workhorse bridge that is contributing to a rural historic district, the mitigation usually involves replacing the bridge with a bridge designed to be context sensitive.  Yet even when a bridge is not contributing to the historic district, a new bridge that is not context sensitive (i.e., does not follow Secretary of Interior Standards) can have an adverse effect to the historic district. Although for both situations the context is established—a rural historic district—there is little guidance on context-sensitive design responses. Increasingly State Historic Preservation Officers (SHPOs) and the National Park Service are taking a landscape perspective on historic resources, leading to more and larger rural historic landscapes/districts. As a result, state DOTs can expect to address historic context considerations in an increasing number of rural bridge replacement projects.
A preliminary survey of published literatures reveals two types of guidance for workhorse bridge aesthetics: (1) presentation of the principles of bridge aesthetics along with scattered examples (e.g., AASHTO’s Bridge Aesthetics Sourcebook Practical Ideas for Short and Medium Span Bridges); or (2) state DOT guidance documents that address urban settings, highway corridors, interchanges, scenic areas, or challenging engineering issues, but not rural historic contexts.


The objective of this research is to develop a practitioner-ready resource of context-sensitive design examples appropriate for workhorse bridges in rural historic districts.

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