Developing an Expanded Functional Classification System for More Flexibility in Geometric Design (2018) / Chapter Skim
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Pages 125-166
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125 PROPOSED FUNCTIONAL CLASSIFICATION SYSTEM This chapter summarizes the various concepts and issues of the proposed functional classification system (referred to as Expanded FCS) and its development.
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126 issues. The Expanded FCS framework determines user needs and orders user levels on a given roadway.
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127 EXPANDED FCS COMPONENTS Context Five distinct contexts are identified in the Expanded FCS that have been determined to represent not only unique land use environments. It is recognized that a more diverse set of contexts may be identified within the built and natural environments.
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128 Figure 41 Expanded FCS context categories The continuum is not perfectly gradual for the determining factors among the five categories and therefore some degree of situational analysis, experience, and professional judgment is required. Furthermore, in real-world situations, discontinuities will exist even when the overall assessment is clear.
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129 significantly)
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130 should be emphasized here that some areas grow faster than projected/planned while others decline faster than expected/planned. This assessment takes some reality testing with stakeholders/officials/professionals to determine the likelihood of future context change.
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131 may be transferred readily from one system to the other, though special attention may be needed in addressing minor collectors. In some cases, it may be applicable to define these roadways as local roads as opposed to collector facilities.
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132 Other Networks Bicycle Networks In addition to the automobile-oriented definitions of roadway type, classifications for bicycles are also proposed to confer structure and priority for bicycle networks. Similar to automobile roadway type classifications, these facilities are categorized based on the network connectivity a facility provides.
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133 amount of time. Ideally, regular and logical spacing between routes of different classifications exists.
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134 of activity. For example, a corridor connecting a university campus with a downtown area may require enhanced sidewalks even if the immediate context may not demand such treatment.
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135 Block Length. The length of blocks affects pedestrian travel demand.
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136 The classification of the roadway types for the driver and bicycles are considered across the entire network and their combination will provide the required coverage to address and balance their needs, based on the 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.
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137 increased mobility is preferred. However, in addition to evaluating the roadway types to serve freight corridors, sensitive context zones, such as urban and urban core areas, should be avoided to minimize interactions between freight and vulnerable road users.
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138 Figure 43 Networks overlay
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139 Incompatibilities between user groups will likely arise throughout the network planning and project development process. When these conflicts occur, the application of an alternate network strategy can be used to identify parallel routes that meet transportation needs for other user groups on routes with more compatible uses.
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140 basis for additional discussions with these stakeholders aiming to identify the relative importance for each facility within the respective network. This process can be relied on CSS principles to define modal priorities and hence establish the network classifications for bicyclist and pedestrian facilities.
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141 Driver Accommodation The metrics used to define the context-roadway interaction for drivers are the target operating speed and the balance between mobility and access. Target Operating Speed Target operating speed is grouped into three categories: Low (<30 mph)
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142 Access and Mobility The typical trade-off between access and mobility presented in the existing classification system is improved in the Expanded FCS to reflect the influence of roadway and context as it changes across the various matrix categories. Access is defined as the frequency of driveways or intersections and is grouped in three categories based on distance between access points: Low (>0.75 mile)
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143 the greater need for access of local roads. The target speed also changes among the categories, with an increasing trend from local to arterial roads.
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144 For principal and minor arterials in rural town and urban contexts, designers can select from a wider range of speed choices (low through medium) for motorized traffic which will help accommodate pedestrians and bicyclists and provide for a safe design for all users.
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145 The proposed functional classification matrix identifies a proposed level of separation that may be considered for each bicycle facility category according to roadway type and context. The following section identifies potential treatments that may be included within each of these separation levels.
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146 Figure 45 Expanded FCS bicyclist interaction matrix Design Considerations Sharrows with narrow lanes may be used when the narrow lane would not cause safety concerns or exceptionally delay traffic flow, including: • Small speed differential between bicycles and vehicles. • Low volume of vehicular or bicycle traffic.
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147 incidents with parked vehicles are not eliminated. Narrower bike lanes (~4 foot)
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148 The AASHTO Guide for the Development of Bicycle Facilities (AASHTO, 2012) and the NACTO Urban Bikeway Design Guide (NACTO, 2011)
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149 local conditions and consistency with future plans for the area or alternative accommodations such as providing shoulders for pedestrian/bicycle usage may be considered. Separation In addition to the facility width, separation of the pedestrian facility from the travel way is also an important consideration.
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150 Expanded FCS Matrix Approach The width of the pedestrian facility and separation from the travel way provided must account for the speed of the motorized traffic and is defined for the anticipated or potential levels of pedestrian traffic for each context and roadway type. The width changes along the context continuum to reflect the traffic volumes anticipated for the facility (Figure 46)
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151 Figure 46 Expanded FCS pedestrian interaction matrix Design Considerations The primary design consideration of pedestrian facilities is the width of the sidewalk or pathway that can comfortably accommodate the demand in a given context. Pedestrian facility widths are defined as minimum per ADA requirements.
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152 expose pedestrians to risk or deter them from walking because they may feel uncomfortable or unsafe. In these instances, a buffer between the traffic and the pedestrians is desirable.
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153 special accommodation, higher priority routes for transit should have smooth turning radii to minimize unnecessary delays at turns. In addition, for high priority or express routes special controlled lanes should be considered for either bus rapid transit or light rail to designate lanes and/or areas for transit service within the right-of-way.
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154 EXPANDED FCS MATRIX The preceding sections identified the specific user-related issues and design considerations that need to be addressed when balancing their needs to deliver a contextually appropriate multimodal design. Figure 47 shows the complete Expanded FCS matrix, which presents the treatment options for each user (driver, bicyclist, and pedestrian)
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155 can be used to identify preliminary requirements that should be given due consideration when assessing current and future roadway context and user needs. In a general project development approach, this process can assist with providing input and refining the purpose and need document, which establishes the framework for the design to be developed.
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156 Each matrix cell provides a range of design options based on defined context zone and roadway type (Figure 47)
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157 4. Use of network overlays such as transit and freight; and 5.
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158 separation. For local connectors, sharrows may be appropriate due to the medium vehicular speeds.
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159 An issue that also merits attention is balancing modal needs and priorities along a corridor, since these may vary along the corridor. These issues are also presented here, and they form the basis for trade-offs among the often-competing needs of each user in order to develop and deliver sound contextually appropriate multimodal solutions.
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160 enhanced facility in the rural context is an off-road facility, since attention should be given for the transition to a sidewalk. Transitioning from the rural town to rural context could follow a reverse order and complement the rural to rural town transition.
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161 For each section of the roadway, a discussion of the driver, bicyclist, pedestrian, transit user and freight is provided that leads to considerations for the designs to be developed. As an example, the discussion for the urban core section is presented here.
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162 Overlays: There is heavy transit demand along the corridor and the lanes need to be designed to accommodate transit buses. There is also some freight demand, mainly small delivery trucks, and this needs to be considered during the final cross section design.
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163 the Expanded FCS matrix providing ranges to accommodate drivers, bicyclists, and pedestrians. Additionally, consideration is given to any transit or freight route information as an overlay.
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164 Driver Accommodation: According to the definitions for an Urban Core Principal Arterial, the roadway should provide low operating speeds (<25 mph)
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165 Evaluating the Pedestrian Crosswalk Score as computed by the Highway Capacity Manual a LOS of C was rated for all approaches. This LOS is based on pedestrian compliance (a function of delay, and width of crossing)
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166 Vehicle LOS for the proposed alternative does degrade, with increased delays leading to a LOS C/D, but all intersections are still shown to operate within capacity during the AM and PM peak hours. Pedestrian Crosswalk LOS is improved from LOS C to LOS B due to the reduced crossing times and delays.
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