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

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Presentation on theme: "INTRODUCTION This chapter presents guidance on the application of geometric design criteria to facilities functionally classified as collector roads and."— Presentation transcript:

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 Volumeconstruction or any number of years within a range from present to 20 years in the future Design Speed70 km/h highways with curves in rolling or mountainous terrain 80 km/hhighways in level terrain see Exhibit 6-1 Sight DistanceExhibit 6-2 for SSD and Exhibit 6-3 for PSD Gradessee Exhibit 6-4

3 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 Slope1.5 –2% for high type pavement 3-7% for low type pavement Sight DistanceExhibit 6-2 for SSD and Exhibit 6-3 for PSD Superelevation  12% for normal roadways  8% for snow and ice regions Number of Lanesdetermined to accommodate for the design volume for the design LOS RURAL COLLECTORS

4 Roadway Widthsee Exhibit 6-5 ForeslopePreferably 1V:4H StructuresThe 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 applicable traffic volume in Exhibit 6-7. Vertical Clearanceat least 4.3 m. RURAL COLLECTORS

5 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 WidthAcquire sufficient ROW at the time of initial construction. Intersection Designsee Chapter 9 RURAL COLLECTORS

6 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 URBAN COLLECTORS

7 Design TrafficThe design traffic should be estimated for at least 10 Volumes and preferably 20 years from the anticipated completion of construction. Design Speed50 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 Distancesee Exhibit 6-2 for SSD see Exhibit 6-3 for PSD GradesShould be as level as practical. Min:0.3%, preferable min. 0.5% Max:5% with sidewalk considered. see Exhibit 6-8 AlignmentFit the existing topography to minimize the needs for cuts or fills in residential areas. URBAN COLLECTORS

8 Cross Slope1.5 –3 % SuperelevationNormally no SE in built-up areas or speed is less 70 km/h or less. When SE is considered, 6% or less Number of LanesTwo moving traffic lanes plus additional width for shoulders and parking are sufficient for most urban collector streets. Roadway Widthsee 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 LanesProvision of parking lanes parallel to the curb is conventional on many collector streets. URBAN COLLECTORS

9 MediansUrban 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 mPaint-striped sections 5.4 – 7.6 mRaised curb section Median openings should be designed with the consideration of SSD. See Chapter 9 for more information CurbsCollector 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. URBAN COLLECTORS

10 DrainageSurface water is gathered by gutters, inlets, catch basins, and storm sewers. Min 0.3% or more for gutters, preferable min 0.5% SidewalksSidewalks 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 sidewalkat least 1.2 m ADAat least 1.5 m Drivewayssee 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. URBAN COLLECTORS

11 Vertical at least 4.3 m Clearance H. Clearance toRoadside 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 WidthSufficient 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. URBAN COLLECTORS

12 Border Area2.4 - 3.3 m including the sidewalk width Intersection Design see Chapter 9 Lighting andsee AASHTO “An Information Guide for Roadway Traffic Control Lighting” and MUTCD Device URBAN COLLECTORS

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