National Academies Press: OpenBook

Developing an Expanded Functional Classification System for More Flexibility in Geometric Design (2018)

Chapter: Chapter 1. Introduction and Research Approach

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Suggested Citation:"Chapter 1. Introduction and Research Approach." National Academies of Sciences, Engineering, and Medicine. 2018. Developing an Expanded Functional Classification System for More Flexibility in Geometric Design. Washington, DC: The National Academies Press. doi: 10.17226/25178.
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Suggested Citation:"Chapter 1. Introduction and Research Approach." National Academies of Sciences, Engineering, and Medicine. 2018. Developing an Expanded Functional Classification System for More Flexibility in Geometric Design. Washington, DC: The National Academies Press. doi: 10.17226/25178.
×
Page 2
Page 3
Suggested Citation:"Chapter 1. Introduction and Research Approach." National Academies of Sciences, Engineering, and Medicine. 2018. Developing an Expanded Functional Classification System for More Flexibility in Geometric Design. Washington, DC: The National Academies Press. doi: 10.17226/25178.
×
Page 3
Page 4
Suggested Citation:"Chapter 1. Introduction and Research Approach." National Academies of Sciences, Engineering, and Medicine. 2018. Developing an Expanded Functional Classification System for More Flexibility in Geometric Design. Washington, DC: The National Academies Press. doi: 10.17226/25178.
×
Page 4

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1 INTRODUCTION AND RESEARCH APPROACH PROBLEM STATEMENT The FCS was developed in the 1970s as a basis for communication between designers and planners (U.S. DOT, 1974). The system sought to establish a common framework for classifying roadways based on mobility and access. Since its inception, the application of the FCS has expanded. It is now used throughout the entire project development process, influencing all work phases, from programming and planning through design and into maintenance and operation decisions. Within design functions in particular, the FCS is often used to define the range of permissive or desired design elements, such as lane width, shoulder width or design speed. The limited range of functional classes, in addition to the severely limited contextual categories (urban and rural), often yields unresponsive designs focused solely on auto-centric travel. Standards based on the FCS often severely limit design choices when developing a transportation solution intended to: 1) meet the purpose and needs of today’s transportation projects, and 2) be adapted to the context in which they are expected to be successful. The FCS has been very useful in the past when the focus was on the automobile and the system was being addressed from a more regional system perspective. In recent years, a significant emphasis has been placed on the development and expansion of flexibility in highway design to address competing project priorities. Flexible design has been the primary goal of Context Sensitive Design/Context-Sensitive Solutions (CSS), Practical Solutions, and Performance Based Practical Design (PBPD) initiatives that have been adopted by many state DOTs in recent years. Both approaches attempt to find the “right-sized” transportation solution for roadway users; the goal is for the solution to fit within the roadway environment. These approaches often examine the imperative of varying design elements needed to balance the unique requirements of the project, including the incorporation of a multimodal presence along the roadway. The narrow focus of the FCS, which considers only mobility and access, as well as its limited contextual definitions (urban and rural), does not provide the dynamic range of design elements and guidance needed to balance other competing needs. While there is a range of design values available, there is no clear way to systematically consider other users and set priorities for the adjustment of the geometric design to achieve an innovative or successful project within a more broadly defined sense of context, user needs, and function. There are two prospective approaches to addressing the issues identified above. First, the FCS needs to be revised to reflect current trends in design practices and roadway uses (e.g.,

2 complete streets). Second, it is critical that a new classification system should be considered that better accommodates CSS and addresses multimodal mobility needs along with other competing factors. State and local agencies require guidance and information to define properly the functional classification of roadways in order to achieve an improved, more contextual geometric design. Moreover, contemporary issues in transportation and community planning, such as the declining balance of the Highway Trust Fund, the growing importance of land redevelopment as a means for local governments to increase its tax base and revenues, and an increasing public desire for transportation projects to accommodate multimodal uses, point to a need to reexamine the FCS and assess the viability of emergent alternative systems and approaches. RESEARCH OBJECTIVES AND APPROACH The objective of this research is to develop a flexible framework to replace the FCS that will facilitate optimal geometric design solutions that account for context, user needs, and functions. The new system will communicate improved information to the designer so that balanced designs can be achieved through documented prioritization of roadway users. Researchers took a two-phased approach toward developing such a framework. The first phase involved a review and synthesis of literature that examined current uses of the FCS, a survey of transportation agencies to define existing issues and possible alternative schemes, and the evaluation and documentation of alternative schemes. In the second phase, the selected approach was detailed further and the potential impacts of the approach on other uses of the FCS were defined. Specifically, the work was completed through the following tasks, accomplished in two phases: Phase I • Task 1: Review of the traditional FCS and identification of its strengths and weaknesses as related to geometric design decisions. • Task 2: Identification and description of existing alternative classification schemes and methods including those used by state DOTs and other agencies as well as the “new urbanism” approaches. • Task 3: Documentation of promising approaches that account for roadway context, function of roadway for various users, and community goals. • Task 4: Development of an interim report.

3 Phase II • Task 5: Development of the panel-approved FCS including implementation approaches and guidance for developing design alternatives. • Task 6: Description of potential impacts of the proposed functional classification on the uses of the current classification system. • Task 7: Preparation of final report. This research led to a FCS to aid and address issues in contextual design. The team accomplished this by first identifying and reviewing existing efforts and FCSs already in place. Then, they developed a FCS that would address current shortcomings of the design process. The proposed FCS (Expanded FCS) can be applied to all roads and could eventually replace the existing classification system. A separate guide has been developed that provides an in-depth discussion of the various components of the Expanded FCS. Two case studies that present the approach to be taken and how the Expanded FCS can be used to aid in the development of contextual design are included. This research strongly suggests a systematic, albeit gradual, effort in replacing the current FCS in order to allow for contextual designs. The results and guide presented here provide the foundation for this effort and showcase an opportunity for process improvement in contextual design. ORGANIZATION OF THE REPORT This report documents the findings of the research work completed during development of the Expanded FCS. The results of this research are included along with recommendations for future research. The components of this report are as follows: • Chapter 2, Literature Synthesis — presents the current knowledge on benefits and other issues relative to functional classification. • Chapter 3, Existing Classification Uses — documents the current uses of the functional classification based on a national survey. • Chapter 4, Classification Schemes — presents the existing classification schemes and discusses their advantages and disadvantages. • Chapter 5, Expanded FCS — presents the proposed FCS as a result of this research and identifies application issues. • Chapter 6, Expanded FCS Implementation — discusses potential impacts from its implementation, and identifies required steps for implementation.

4 • Chapter 7, Conclusions — includes a summary of the study objectives, project findings, and recommendations for future research work. • NCHRP Research Report 855: An Expanded Functional Classification System for Highways and Streets — includes a guide for applying the Expanded FCS and two case studies demonstrating its application.

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TRB's National Cooperative Highway Research Program (NCHRP) Web-Only Document 230: Developing an Expanded Functional Classification System for More Flexibility in Geometric Design, which documents the methodology of NCHRP Research Report 855: An Expanded Functional Classification System for Highways and Streets builds upon preliminary engineering of a design project, including developing the purpose and need.

In particular, NCHRP Web-Only Document 230 provides additional contexts beyond urban and rural, facilitates accommodation of modes other than personal vehicles and adds overlays for transit and freight.

Two case studies illustrating an application of the expanded system to actual projects are included.

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