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Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. An Expanded Functional Classification System for Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/24775.
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Page 2
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. An Expanded Functional Classification System for Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/24775.
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Page 2
Page 3
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. An Expanded Functional Classification System for Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/24775.
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Page 3
Page 4
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. An Expanded Functional Classification System for Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/24775.
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Page 4
Page 5
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. An Expanded Functional Classification System for Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/24775.
×
Page 5
Page 6
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. An Expanded Functional Classification System for Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/24775.
×
Page 6
Page 7
Suggested Citation:"Introduction." National Academies of Sciences, Engineering, and Medicine. 2018. An Expanded Functional Classification System for Highways and Streets. Washington, DC: The National Academies Press. doi: 10.17226/24775.
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Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

1 This guidance has been developed to demonstrate the application of the Expanded Functional Classification Sys- tem (Expanded FCS) for highways and streets. The Expanded FCS provides a flexible framework, which can replace the existing functional classification scheme, in order to facilitate optimal geometric design solutions that take into account environmental context, road functions, and user needs. This system builds upon existing efforts of state departments of transportation (DOTs) that have initiated and implemented a new classification system to address contextual multimodal deficiencies of the existing classification system. The major objective of the Expanded FCS is to provide enhanced information to designers to better inform the design decision process through the process shown in Figure 1. This enhanced information is provided by increasing the resolu- tion of a roadway’s design context to enable understanding of the role the roadway plays within the community; identify- ing the role of the roadway within the local, city, and regional transportation network; and identifying the multiple roadway user groups and their priority within the design corridor. [In this document, the term “roadway” is considered to include all facilities intended for travel in the right-of-way (e.g., travel lanes, shoulders, bicycle lanes, sidewalks).] Having this information within the expanded framework of the functional classification system gives practitioners a practical tool for determining appropriate design criteria and elements by helping them better understand the impacts of the tradeoffs necessary to balance user needs and safety, and address other community issues. Proper contextual roadway designs require an understanding of the function of the roadway within its current and expected future context and the needs of the potential roadway users. The Expanded FCS and associated design matrix can assist in identifying the preliminary requirements for proper consider- ation of roadway context and user needs. This approach pro- vides the framework for determining user needs and ordering Introduction Figure 1. Implementation steps for Expanded FCS.

2 An Expanded Functional Classification System for Highways and Streets user levels on a given roadway. It assumes the planner/designer can develop alternative system/ network strategies for meeting all user needs. This process can assist in providing input and refine- ment to the purpose and need document, which establishes the framework for the design to be developed. In the end, the final balancing of facilities to accommodate user needs becomes part of the process of following project development principles for achieving context sensitive solutions. Relationship to Other Guides This guidance supplements and expands on policies, guides, and standards commonly used by designers and planners of state and local transportation agencies and engineering and public works divisions. It provides a simple yet dynamic approach that integrates several processes and tools into a comprehensive planning and design framework. The Expanded FCS reflects current design thinking and can be used in conjunction with other important publications including A Policy on Geometric Design of Highways and Streets (AASHTO 2011); Guide for the Planning, Design and Operation of Pedestrian Facilities (AASHTO 2004b); Guide for the Development of Bicycle Facilities (AASHTO 2012); A Guide for Achieving Flexibility in Highway Design (AASHTO 2004a); Guide for Geometric Design of Transit Facilities on Highways and Streets (AASHTO 2014); Urban Street Design Guide (NACTO 2013); Urban Bikeway Design Guide (NACTO 2011); and Designing Walkable Urban Thoroughfares: A Context Sensitive Approach (ITE and Congress for the New Urbanism 2010), as well as complementary state department of transportation design policies and manuals, local municipal street design standards, urban design guides, and guidance published by other standard-setting organizations. This guidance adds to information found in the previously mentioned publications by pro- viding comprehensive guidance on the following: 1. Expanding the context definitions beyond the binary urban/rural distinction and recognizing the network importance of roadway types. 2. Identifying the multiple roadway user groups and their priority. 3. Defining a balanced approach for potential design ranges by considering a broader set of factors for planning and designing roadways. 4. Considering other modal (transit and freight) overlays and their implications for roadway design. 5. Understanding the purpose and need for a project in order to develop design alternatives to accommodate drivers, bicyclists, pedestrians, and transit/freight users in an efficient and contextually appropriate design. Expanded FCS Overview Context The five distinct contexts identified in the Expanded FCS have been determined to not only represent unique land use environments, but also identify distinctions that require wholly dif- ferent geometric design practices in terms of desired operating speeds, mobility/access demands, and user groups. The context categories (illustrated in Figure 2) are as follows: 1. Rural: Areas with lowest density, few houses or structures (widely dispersed or no residential, commercial, and industrial uses), and usually large setbacks. 2. Rural Town: Areas with low density but diverse land uses with commercial main street char- acter, potential for on-street parking and sidewalks, and small setbacks. 3. Suburban: Areas with medium density, mixed land uses within and among structures (includ- ing mixed-use town centers, commercial corridors, and residential areas), and varied setbacks. Proper contextual roadway designs require an understanding of the function of the roadway within its current and expected future context and the needs of the potential roadway users.

Introduction 3 4. Urban: Areas with high density, mixed land uses and prominent destinations, potential for some on-street parking and sidewalks, and mixed setbacks. 5. Urban Core: Areas with highest density, mixed land uses within and among predominately high-rise structures, and small setbacks. Roadway Types Functional classification has, for decades, relied on three general thoroughfare types for clas- sification: arterials, collectors, and locals (more recently, arterials have been further subdivided into principal and minor, resulting in four classification types currently being used). Decades of familiarity with these terms, and many federal funding mechanisms being based in whole or in part on these four classifications, have resulted in continued use of the same labels. The roadway types used in the Expanded FCS are based on the function of the roadway within its network and the connectivity the roadway provides among various centers of activity. Net- work function is defined based on the regional and local importance of the roadway to vehicle Rural Rural Town Suburban Urban Urban Core Figure 2. Five context categories.

4 An Expanded Functional Classification System for Highways and Streets movement. Connectivity identifies the types of activity centers and locales that are connected with the particular roadway. The Expanded FCS roadway types (illustrated in Figure 3) are as follows: 1. Interstates/Freeways/Expressways: Corridors of national importance connecting large centers of activity over long distances. 2. Principal Arterials: Corridors of regional importance connecting large centers of activity. 3. Minor Arterials: Corridors of regional or local importance connecting centers of activity. 4. Collectors: Roadways of lower local importance providing connections between arterials and local roads. 5. Locals: Roads with no regional or local importance for local circulation and access only. The Expanded FCS will not address context types for Interstates, Freeways, and Express- ways because designs for these facilities are based on federally developed standards with little flexibility. The primary difference between the Expanded FCS and existing functional classification system is the absence of differentiation between minor and major collectors. These roadway types were combined because of the inability to sufficiently distinguish design, operating, and modal characteristics of the two types. Therefore, existing classifications of roadways may be readily transferred from one system to the other; however, special attention may be needed in addressing minor collectors, as in some cases these roadways may be better classified as local roads. Note that the major/minor collector distinction currently serves as the dividing line between eligible-for-federal-aid and ineligible-for-federal-aid roadways within rural areas. Adoption of the Expanded FCS would require a new definition for eligible/ineligible-for-federal- aid roadways. Roadway Users The Expanded FCS identifies three user groups: drivers, bicyclists, and pedestrians. The term “drivers” refers to automobile drivers; drivers for transit and freight are handled as an overlay Figure 3. Four of the five Expanded FCS roadway types.

Introduction 5 (discussed in the next section). Fundamental design accommodation elements for each mode are also identified, and design ranges for each are provided based on the overall roadway network type. Various user needs should be identified from the outset and considered when balancing and making the necessary tradeoffs among design elements in order to develop contextually appropriate multimodal solutions. Driver accommodations are identified as follows: • Operating speed. • Mobility (freedom of movement and delay within the traffic stream). • Access to adjacent properties/roadways. Similar to automobile roadway types, bicycle facility classes, where established, identify pri- ority and network importance of bicycle facilities. The primary difference in automobile and bicycle networks is the scale of the bicycle network is smaller, consistent with the overall range of bicyclists. Three standard bicycle facility classes have been established: • Citywide connector connects the city or major activity centers and stretches over several miles. • Neighborhood connector connects neighborhoods or sub-areas, which establishes connec- tions to higher-order facilities or local activity centers. • Local connector provides internal connections of short lengths within neighborhoods. Bicycle facility designs are generally categorized based on the amount of separation between the facility and motorized traffic, which varies according to the bicycle route’s classification and the roadway type it is on. Bicycle facility designs are categorized as follows: • High separation: Facility is physically separated from traffic by a physical barrier or lateral buffer. • Medium separation: Facility is a dedicated space adjacent to motorized traffic. • Low/No separation: Facility is joint use for motorized and non-motorized traffic. Pedestrian facilities are generally categorized according to their width. This document uses the following categories: • Site-specific facilities for pedestrians, due to absence or rare occurrence of pedestrians. • Minimum width—the minimum required width based on local ADA requirements. • Wide width—wider than the minimum required width for a pedestrian facility. • Enhanced width—wider than the wide width to accommodate congregating groups of pedestrians, street furniture, and pedestrian activities. In addition to the facility width, separation of the pedestrian facility from the travel way is an important consideration. However, this design element is primarily dependent on the design speed of the automobile facility rather than on the level of activity on the roadway. Typically, medium- and high-speed automobile facilities will require pedestrian facilities to be separated from the travel way by a tree lawn, landscaped buffer, bicycle lanes, or parking areas. For low- speed automobile facilities, the sidewalk may be attached to the curb, directly adjacent to the travel way without a need for a buffer area. The correlation of context, roadway types, and users results in the Expanded FCS matrix (Figure 4). This allows for the development of a multimodal, context-based design with some degree of flexibility. Each matrix cell defines the various users (drivers, bicyclists, and pedestri- ans) and identifies which characteristics are to be balanced. The accommodation of drivers and bicyclists is considered across the entire network and reflected in the roadway-type classification of each facility. The combination of facilities will provide the required coverage to address and balance the needs of both user groups based on the

6 An Expanded Functional Classification System for Highways and Streets roadway context. Pedestrian needs are also defined based on the roadway context, but there is no specific network classification for facilities to accommodate their needs. It should be also noted that a corridor may transition into different contexts over its length and this will be reflected in the design considerations and cross sections. Overlays In addition to the context, roadway type, and user groups presented in the matrix, other design needs may be addressed through the application of overlays to handle special users, such as transit and freight, or other demands. Overlays add further complexities and require their design demands to be accounted for in the solutions developed. Users of the Expanded FCS could also develop additional overlays as appropriate to address specific area needs. Application When approaching a corridor design, the design team can utilize the Expanded FCS to under- stand the role the roadway will play both in the environment in which it will be constructed and within the network. Various user groups that must be accommodated within the roadway are also identified, so that their competing needs and spatial demands may be considered. To assist in balancing and prioritizing these needs, the importance of the roadway within the individual network of each road user is also identified. This approach assumes that the Expanded FCS will be initially applied to all state-maintained roadways and replace the existing functional classification system. It is anticipated that the con- text and roadway types for each roadway will be periodically reviewed and revised (consistent with current practices) as needed to accommodate change. It is also possible that a transportation agency may elect to implement Expanded FCS in a staged approach where the changes are considered at a project level. Once a project is started, the project team will have to review the context and roadway-type designations and determine whether these are applicable or require any adjustments. Once this determination is made, the project team can proceed with validating each component of the classification process, includ- ing context, roadway type, and users, and proceed in developing a contextual design utilizing context sensitive solutions (CSS) to balance project needs and community values. This process assumes that the project team will be diligent in determining the complexities of the context, Figure 4. Expanded FCS framework user matrix.

Introduction 7 both current and future, as well as all other subtleties associated with the social and natural envi- ronment surrounding the project. Once the appropriate matrix cell that addresses the context– roadway environment is defined, the project team could start developing the preliminary designs considering community comprehensive plans including the future land use plan, and any other pertinent information (including zoning ordinances) in order to develop an evolving design that could address potential changes in the roadway context. The need for a robust CSS process (involving all stakeholders) is integral to the successful implementation of the Expanded FCS and development of contextually appropriate designs. Balancing modal needs is central to Expanded FCS. It is understood that there is the possi- bility that the designer will not be able to provide the best facilities for all the users at all times and at the same location in all roadways. There will be instances where the mobility needs for some groups require adjustments and/or consideration of alternative routes as well as the use of revised system overlays. On high-speed arterials, for example, bicycles and pedestrians may need to be accommodated on a parallel roadway with lower speeds where the proper designs could be attained to accommodate their mobility needs. Likewise, a corridor with high bicycle demand and mobility needs may require the presence of bicycle facilities that would lower speeds and possibly reduce the number of available vehicle lanes if there is limited right-of-way. Design considerations for how to achieve this are presented in the Modal Considerations and Accom- modations chapter. Figure 5 shows the overall matrix concept identifying potential levels of use, i.e., typical user priorities, for each possible mode. Typical uses are based on current traffic trends and exist- ing networks, and they should not be viewed as modal accommodation for each context and roadway-type combination. Figure 5. Typical user priorities in the Expanded FCS.

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TRB's National Cooperative Highway Research Program (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, it 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. Accompanying the report is 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.

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