Bridges are important functional and historic structures in both urban and rural settings. In CSS projects, designers are addressing the aesthetic design of a bridge, its linkages to the surrounding context at each end of the bridge, and the functions that bridges can serve for pedestrians, bicyclists.
Bridge Design Elements: Introduction "...bridges are viewed from two perspectives. Traveling
over the bridge deck, the driver of a vehicle sees the travelway, bridge railings, and
the view to either side. If the bridge crosses over another roadway, water or land
both on its side and underneath can also be viewed from this perspective. It is
important for bridge designers to keep in mind that these two perspectives may
require consideration of additional aesthetic treatments for the bridge." more...
Flexibility in Highway Design
General Guidelines for the Geometrics of Bridge Design "Bridges and other related major structures play an important role in defining the manner in which a highway affects the aesthetic, scenic, historic, and cultural resources of the corridor within which it is located....The geometric criteria in the AASHTO Green Book for new or replacement bridges deal primarily with the width of the bridge deck and its relationship to approach
roads. Early design coordination is important when establishing the width of a new or replacement bridge and in determining its horizontal and vertical alinement. Road engineers, architects, and landscape architects, as well as members of the community, can provide input to help the bridge designer determine the appropriate geometric dimensions and overall appearance of the bridge....In addition to determining the width of the travelway, a bridge designer must consider the need for pedestrian and non-vehicular traffic over the bridge and the most appropriate method for accommodating it."
Flexibility in Highway Design
Acadia Bridge Diagrams
The following charts and diagrams from the Historic American Engineering Record (HAER) show roads, bridges, and design principles in Maine's Acadia National Park. Search the Resource Bank for HAER to find more historical drawings from this organization.
-- Historic American Engineering Record (HAER)
Bridges: Flexibility in the AASHTO Guidelines The replacement or retention of bridges having historic or aesthetic value or the design of bridges on very low-volume roads may justify traveled way widths less than the indicated minimum AASHTO Green Book (2) values. The width evaluation should be made by a design professional on an individual basis as part of the retention or removal decision-making process. Once the retention or replacement width decision is made, structural details, including bridge rails, should conform to AASHTO bridge specifications. more...
A Guide for Achieving Flexibility in Highway Design
Article / Paper / Report
Historic Bridge Manual - Texas DOT
The manual provides procedures that should be followed when dealing with historic bridges and serves as a reference regarding applicable laws, regulations, policies, and guidelines. In addition to historic bridge issues, the manual provides a brief discussion of the Unified Transportation Program (UTP), the Highway Bridge Replacement and Rehabilitation Program (HBRRP), and the project selection process known as the Texas Eligible Bridge Selection System ( TEBSS).
Danville-Riverside Bridge and Approach - Pennsylvania Danville-Riverside, PA
The project involved replacement of an existing two-lane Parker Through Truss bridge built in 1904 spanning the Susquehanna River, with a new 1,440 foot-long bridge with weathered steel haunched girders. The approach to the old bridge from Danville was on Mill Street, the center of the town's downtown commercial area. The final alignment for the new bridge on this side of the river directs traffic under two blocks of the West Market Street Historic District one block west of Mill Street, creating a 320 foot-long cut and cover structure before transitioning onto the four-lane Continental Boulevard which links to other major traffic routes. The lessons learned in this project process have helped shape PENNDOT's evolving pro-active effort to involve stakeholders earlier and more meaningfully in project planning, design and development.
Merritt Parkway: Greenwich, Connecticut Greenwich, CT
Much has been written and reported about the safety improvements and landscape restoration of the Merritt Parkway which started in the 1990s in Greenwich, Connecticut, a unique community that shaped the approach that was ultimately taken to improve this roadway. The community's influence started long before any formal design process was undertaken, and in fact, and was instrumental in motivating the context sensitive design approach (although not called such at the time). Overall this project can be considered an excellent example of how a road represents so much more to a community than simply a transportation conduit. The future of this roadway was community driven and while the DOT provided the leadership and expertise to accomplish the improvements, their use of other professionals, such as landscape architects and historians, improved the final result. This case study focuses on the initial context sensitive design process which preceded the first improvements to the highway and revitalization of the setting.
Smiths Creek Covered Bridge - Delaware DE
Bridge 9 (Smiths Bridge) is a one-lane wide, three-span steel beam bridge with timber deck and railing with a superstructure dating from 1962 when it was rebuilt following a fire. The original superstructure was a single-span timber covered bridge constructed in 1839. The substructure consists of stone abutments dating back to the original 1839 bridge and stone faced concrete piers that were constructed in the1950's when steel beams were added for support. The substructure is considered to be a contributing element to the historic district in which the bridge lies. The latest condition evaluation reports that the bridge deck is in poor condition, with the superstructure and substructure in fair condition. Based on the condition of the bridge, the scope of work was determined to include replacement of the superstructure and rehabilitation of the substructure.
Historic Columbia River Parkway Columbia River Gorge, OR
The first paved highway in the northwestern United States, the Columbia River Highway was conceived, designed, and constructed as both a scenic attraction and as a means of facilitating economic development along the Columbia River corridor between the Pacific Ocean and the areas to the east of the Cascade Mountains. The history of the development, decline, and continuing rebirth of the Columbia River Highway is particularly instructive to the highway engineering community as we approach the beginning of a new century and a future of increasing reliance on the rehabilitation and restoration of existing infrastructure instead of the construction of new highways. This study also illustrates the manner in which state and local governments can preserve and enhance existing highways that possess unique scenic and historic qualities within the framework of modern design criteria.
Bridges and overpasses can be positive and interesting features along a byway. The design should take into account the context of the landscape and reflect its historic, rural, or urban character. Choose materials and colors that complement the surrounding landscape. Consider restoring historic bridges for their important contribution to the character of their byways.
Bridges and overpasses provide vehicle and pedestrian access. Passage for fish and wildlife on and under these structures should be incorporated into the design where appropriate. Bridge piers and substructures should not encroach on the stream channel. Aesthetic railings or walls can be selected that meet requirements.