Developing an Expanded Functional Classification System for More Flexibility in Geometric Design (2018) / Chapter Skim
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Pages 5-28
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5 LITERATURE SYNTHESIS The purpose of this literature review is to synthesize pertinent information, specifically, to examine the purpose and need that led to the development of the FCS, and to understand current FHWA thinking and policies. Additional focus is placed on critiques and analyses of roadway classification within the modern transportation sector.
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6 Figure 1 Mobility and access proportion of service by functional class (FHWA, 1982) This general classification has driven functional classification programs since their emergence in the mid-twentieth century.
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7 management tool during this period, with state transportation agencies adopting functional classification as the basis for defining statewide systems that included roads outside of those on the nationally recognized system (FHWA, 1982)
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8 3. Other Principal Arterials; 4.
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9 Table 2 FHWA urban area types defined by population range FHWA Area Definition Population Range Allowed Urban Area Boundary Adjustments Urban Area 5,000+ Yes Small Urban Area (From Clusters) 5,000-49,999 Yes Urbanized Area 50,000+ Yes FHWA does not publish its own roadway design standards for the national system.
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10 The universal application of the FCS has enabled its integration into many facets of local operations. Uses include local access management and traffic calming eligibility; grouping for operational and safety performances; and directing built form through local land use and/or zoning documents, subdivision regulations, and site development standards.
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11 • Maintenance -- Functional classification often influences resurfacing cycles, which is related to asset management and project prioritization. The classification of a roadway also affects general maintenance and snow/ice removal during inclement weather.
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12 Second, each manual was examined for whether there exists guidance for design element values in accordance to the classification system adopted. All manuals provide some guidance, provided in different formats.
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13 Figure 2 Example of Tennessee DOT guidance
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14 Several states have begun developing additional guidance policy documents for context sensitive designs, encouraging highway designers to incorporate environmental and community considerations into the interpretation of roadway design guidance. However, multiple states continue to use Green Book-based approaches that define functional classification, establish design values for each roadway component based on the its guidance, and generally offer little flexibility in terms of how these design values are to be interpreted or modified outside of a design exception or waiver process.
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15 scope and intent, as with its influence on geometric design, or through improper application by engineers and policymakers. Issues with the system are identified and discussed in the following section.
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16 inflexibility in roadway design -- especially in urban streets -- that limits an agency's inclination to explore multiple designs for a project. In some cases, guidance explicitly states that the design values established in these manuals are minimum values that should be met or be exceeded to achieve what is perceived the safest and most efficient design.
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17 Hall (2003) identified four key factors explaining the conflicts between the Green Book policies and walkable, New Urbanism design: 1.
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18 Access vs. Mobility Those with even preliminary knowledge of the FCS will be familiar with the balancing of mobility and land access as shown in Figure 1.
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19 mobility corridors, in practice much of the land fronting arterials is zoned for commercial uses that require numerous access points. The problem of serving this dual function illustrates one of the shortcomings of using functional classification as a primary means of network planning (ARRB, 1979)
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20 Figure 4 US 460 at Salyersville, KY Urban Networks In a rural roadway system, roads typically follow a tributary nature as classified by the FCS. However, in urban areas, due to the higher density of roadways, parallel and redundant routes (especially in a grid system)
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21 Figure 6 however, shows the street system of Salt Lake City, UT, which is based entirely on a grid system. In this network, parallel and redundant routes exist for all directions.
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22 operating speeds, volumes, intersection spacing, and travel lengths for their newly developed alternative classification scheme (NJDOT & PADOT, 2008)
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23 began to voice concerns about the adverse environmental impacts of expanding the road network. This resulted in the passage of the National Environmental Policy Act in 1969, which had significant implications for roadway design and construction.
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24 14. Use agency resources effectively.
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25 merely optimizing individual project outcomes. This approach aims to achieve a solution that would result in the maximum rate of return on the individual project and not the maximum return possible.
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26 As with any project development process, the ultimate objective is to develop a project that addresses mobility, safety, community, and environmental goals. The Practical Solutions approach encourages the designer to use creative design and move away from the typical crosssection concept.
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27 number of typical elements to consider when designing a Complete Street, and they may vary based on the roadway type and area context, including: pedestrian facilities (sidewalks, shareduse paths, crosswalks, median islands for refuge, pedestrian signals) ; bicycle facilities (paved shoulders, bicycle lanes, shared-use paths)
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28 is evidenced by its failure to recognize other modes of transportation, and through the limited context definition provided by the urban/rural classification. While procedures are in place to address these issues, such as the use of design exceptions, it is apparent that these are the exceptions -- not the rule.
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