FOREWORD

This Guide is about designing highways that incorporate community values and are safe, efficient, effective mechanisms for the movement of people and goods. It is written for highway engineers and project managers who want to learn more about the flexibility available to them when designing roads and illustrates successful approaches used in other highway projects. It can also be used by citizens who want to gain a better understanding of the highway design process.

Congress, in the Intermodal Surface Transportation Efficiency Act (ISTEA) of 1991 and the National Highway System Designation (NHS) Act of 1995, maintained a strong national commitment to safety and mobility. Congress also made a commitment to preserving and protecting the environmental and cultural values affected by transportation facilities. The challenge to the highway design community is to find design solutions, as well as operational options, that result in full consideration of these sometimes conflicting objectives.

To help meet that challenge, this Guide has been prepared for the purpose of provoking innovative thinking for fully considering the scenic, historic, aesthetic, and other cultural values, along with the safety and mobility needs, of our highway transportation system. This Guide does not establish any new or different geometric design standards or criteria for highways and streets in scenic, historic, or otherwise environmentally or culturally sensitive areas, nor does it imply that safety and mobility are less important design considerations.

When Congress passed ISTEA in 1991, in addition to safety, it emphasized the importance of good design that is sensitive to its surrounding environment, especially in historic and scenic areas. Section 1016(a) of ISTEA states:

If a proposed project ...involves a historic facility or is located in an area of historic or scenic value, the Secretary may approve such project ...if such project is designed to standards that allow for the preservation of such historic or scenic value and such project is designed with mitigation measures to allow preservation of such value and ensure safe use of the facility.

Aesthetic, scenic, historic, and cultural resources and the physical characteristics of an area are always important factors because they help give a community its identity and sense of place and are a source of local pride.
In 1995, Congress reemphasized and strengthened this direction through the NHS Act, which states, in section 304:

A design for new construction, reconstruction, resurfacing... restoration, or rehabilitation of a highway on the National Highway System (other than a highway also on the Interstate System) may take into account...[in addition to safety, durability and economy of maintenance]...

1. the constructed and natural environment of the area;
2. the environmental, scenic, aesthetic, historic, community, and preservation impacts of the activity; and
3. access for other modes of transportation.

The National Highway System (NHS) consists of approximately 161,000 miles of roads, including the Interstate System, or 4 percent of the total highway mileage. The primary purpose of the NHS is to ensure safe mobility and access. By emphasizing the importance of good design for these roads, Congress is saying that careful, contextsensitive design is a factor that should not be overlooked for any road.

A Policy on the Geometric Design of Highways and Streets (Green Book), published by the American Association of State Highway and Transportation Officials (AASHTO), contains the basic geometric design criteria that establish the physical features of a roadway. This Guide is correlated to a large extent to the Green Book because that is the primary geometric design tool used by the highway design community. Like the Green Book, this Guide contains sections on functional classification, design controls, horizontal and vertical alinement, crosssection elements, bridges, and intersections. There are many good projects highlighted in this Guide that were achieved working within the parameters of the Green Book to obtain safety and mobility and to preserve environmental and cultural resources. These projects used the flexibilities that are available within the criteria of the Green Book. These projects also used a comprehensive design process, involving the public and incorporating a multidisciplinary design approach early and throughout the process.

If highway designers are not aware of opportunities to use their creative abilities, the standard or conservative use of the Green Book criteria and related State standards, along with a lack of full consideration of community values, can cause a road to be out of context with its surroundings. It may also preclude designers from avoiding impacts on important natural and human resources.
This Guide encourages highway designers to expand their consideration in applying the Green Book criteria. It shows that having a process that is open, includes public involvement, and fosters creative thinking is an essential part of achieving good design. This Guide should be viewed as a useful tool to help highway designers, environmentalists, and the public move further along the path to sensitively designed highways and streets by identifying some possible approaches that fully consider aesthetic, historic, and scenic values, along with safety and mobility. It also recognizes that many designers have been sensitive to the protection of natural and humanmade resources prior to ISTEA.

The decision to use and apply the concepts illustrated and discussed in the Guide for any specific project remains solely with the appropriate State and/or local highway agencies. In addition, while many of the concepts discussed will clearly aid the decision process, it must be recognized that changes in the design or design criteria will not always resolve every issue to a mutual level of satisfaction.