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INTRODUCTION

INTRODUCTION. This chapter presents guidance on the application of geometric design criteria to facilities functionally classified as collector roads and streets.

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INTRODUCTION

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  1. INTRODUCTION This chapter presents guidance on the application of geometric design criteria to facilities functionally classified as collector roads and streets. Local roads and streets serve a dual function: collecting traffic for movement between arterial streets and local roads and providing access to abutting properties. Traffic volume greater than 400 veh/day is one of the design criteria for design of local roads and streets. Roads less than 400 veh.//day are not applicable to the design criteria in this chapter. AASHTO is working on the design of these types of roads. This chapter discusses two types of roadways: Rural Collectors and Urban Collectors.

  2. RURAL COLLECTORS Two lane collector highways constitute an important part of the rural highway system. Design Traffic Design year is 20 years from the date of completion of Volume construction or any number of years within a range from present to 20 years in the future Design Speed 70 km/h highways with curves in rolling or mountainous terrain 80 km/h highways in level terrain see Exhibit 6-1 Sight Distance Exhibit 6-2 for SSD and Exhibit 6-3 for PSD Grades see Exhibit 6-4

  3. RURAL COLLECTORS Alignment Horizontal and vertical alignment should complement each other and should be considered in combination to achieve appropriate safety, capacity, and appearance for the type of improvement proposed. Cross Slope 1.5 –2% for high type pavement 3-7% for low type pavement Sight Distance Exhibit 6-2 for SSD and Exhibit 6-3 for PSD Superelevation  12% for normal roadways  8% for snow and ice regions Number of Lanes determined to accommodate for the design volume for the design LOS

  4. RURAL COLLECTORS Roadway Width see Exhibit 6-5 Foreslope Preferably 1V:4H Structures The minimum design loading for bridges on collector roads should be MS-18. The minimum roadway width for new and reconstruction bridges should be one shown in Exhibit 6-6. Bridges to An existing bridge may remain in place when its structural Remain in capacity in terms of design loading and roadway width Place are at least equal to the values shown for the applicabletraffic volume in Exhibit 6-7. Vertical Clearance at least 4.3 m.

  5. RURAL COLLECTORS H. Clearance To Obstructions  3 m from ETW for 70 km/h or less Refer to AASHTO Roadside Design Guide for 80 km/h or more ROW Width Acquire sufficient ROW at the time of initial construction. Intersection Design see Chapter 9

  6. URBAN COLLECTORS Serves as a public facility for vehicle, bicycle and pedestrian travel and accommodates public utility facilities within the ROW. The development or improvement should be considered in the comprehensive community development plan. The function of urban collectors is providing equally services for mobility and access. Criteria: Minimizing conflict points Providing adequate storage length for all turning movements Minimizing conflicts with pedestrian and bike users Coordinating driveway locations on opposite side of roadway Locating signals to meet progression needs Maintaining efficient circulation while providing adequate ingress and egress capacity

  7. URBAN COLLECTORS Design Traffic The design traffic should be estimated for at least 10 Volumes and preferably 20 years from the anticipated completion of construction. Design Speed 50 km/h or higher should be used. Very often the design speed is not significant when the urban street grids have closely spaced intersections Sight Distance see Exhibit 6-2 for SSD see Exhibit 6-3 for PSD Grades Should be as level as practical. Min: 0.3%, preferable min. 0.5% Max: 5% with sidewalk considered. see Exhibit 6-8 Alignment Fit the existing topography to minimize the needs for cuts or fills in residential areas.

  8. URBAN COLLECTORS Cross Slope 1.5 –3 % Superelevation Normally no SE in built-up areas or speed is less 70 km/h or less. When SE is considered, 6% or less Number of Lanes Two moving traffic lanes plus additional width for shoulders and parking are sufficient for most urban collector streets. Roadway Width see Exhibit 6-5. Note that the roadway width is the sum of the widths of ultimate lanes for moving traffic, parking , and bikes, including median width where appropriate. Parking Lanes Provision of parking lanes parallel to the curb is conventional on many collector streets.

  9. URBAN COLLECTORS Medians Urban collector streets designed for four or more lanes should include width for an appropriate median treatment, where practical. 0.6 – 1.2 m Paint-striped separation 0.6 – 1.8 m narrow raised-curbed sections 3.0 – 4.8 m raised curb sections 3.0 – 4.8 m Paint-striped sections 5.4 – 7.6 m Raised curb section Median openings should be designed with the consideration of SSD. See Chapter 9 for more information Curbs Collector streets normally are designed with curbs to allow greater use of available width and for control of drainage, protection of pedestrians and delineation. Vertical curbs with heights of 150 mm or more should be offset by 0.3 – 0.6 m from the edge of ETW.

  10. URBAN COLLECTORS Drainage Surface water is gathered by gutters, inlets, catch basins, and storm sewers. Min 0.3% or more for gutters, preferable min 0.5% Sidewalks Sidewalks should be provided along both sides of urban collector streets that are used for pedestrian access to schools, parks, shopping areas, and transit stops and along all collectors in commercial areas. At least one side for residential area. Width of sidewalk at least 1.2 m ADA at least 1.5 m Driveways see AASHTO Guide for the Planning, Design, and Operation of Pedestrian Facilities. Roadway Width curb-to-curb width for new bridges. See Exhibit 6-6 and 6-7 for bridge widths on urban collector streets.

  11. URBAN COLLECTORS Vertical at least 4.3 m Clearance H. Clearance to Roadside obstructions on urban collector streets should Obstructions preferably be located at or near the right-of-way line and outside of the sidewalk. 0.5 m or more for streets without shoulders but with curbs ROW Width Sufficient to accommodate the ultimate planed roadway, including median, shoulder, grass border, sidewalk, bicycle facilities, public utilities, and outer slopes. Provision for Utilities Use of the ROW by utilities should be planned to minimize interference with traffic using the streets.

  12. URBAN COLLECTORS Border Area 2.4 - 3.3 m including the sidewalk width Intersection Design see Chapter 9 Lighting and see AASHTO “An Information Guide for Roadway Traffic Control Lighting” and MUTCD Device

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