02 - Chapter-2 - Chapter 2 Geometric Design Manual-2002...

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Unformatted text preview: Chapter 2 Geometric Design Manual-2002 Summary of Standards (WKLRSLDQ 5RDGV $XWKRULW\ 3DJH 6 800$5< 2) 6 7$1'$5'6 $1' ' (3$5785(6 )520 6 7$1'$5'6 ,QWURGXFWLRQ Geometric design the process whereby the layout of the road through the terrain is designed to meet the needs of the road users. The principal geometric features are the road cross-section and horizontal and vertical alignment. Appropriate standards and combinations of geometric design elements should fulfill the following objectives: ¾ Topography, land use and physical features. ¾ Environmental considerations. ¾ Road safety considerations. ¾ Road function and control of access. ¾ Traffic volume and capacity. ¾ Design speed and other speed controls. ¾ Design vehicle and vehicle characteristics. ¾ Economic and Financial considerations. ¾ Alternative construction technologies. 'HVLJQ 6WDQGDUGV The design standards to be used for roads of various traffic volumes (AADT) are summarized in the several following tables. Of these, Table 2-1 presents an overview of design standards relating to road functional classification and traffic volumes, and illustrates the split between paved and unpaved standards. Tables 2-2 to 2-11 give several parameters of the Ethiopian Roads Authority’s ten design standards, reflecting the government policy of design flexibility and emphasis on labor-based techniques. These standards apply to divided highways, trunk and link roads, main access and collector roads, and feeder roads. Finally, Table 2-12 shows the variability of the shoulder widths for the different design standards, including parameters associated with terrain and urban sections. The determination of each particular standard item is discussed further in this manual. 'HSDUWXUHV IURP 6WDQGDUGV It is anticipated that there may be situations where the designer will be compelled to deviate from these standards. An example of a Departure from Standard is the inclusion of a switchback or the use of a gradient greater than the desirable value. Where the designer departs from a standard, he must obtain written approval from ERA. The Designer shall submit the following information to ERA: Chapter 2 Summary of Standards Geometric Design Manual-2002 3DJH (WKLRSLDQ 5RDGV $XWKRULW\ ¾ The number, name, and description of the road ¾ The facet of design for which a Departure from Standards is desired; ¾ A description of the standard, including normal value, and the value of the Departure from Standards ¾ The reason for the Departure from Standards, and ¾ Any mitigation to be applied in the interests of safety. The Designer must submit all major and minor Departures from Standards to the Design and Research Division Manager for evaluation. If the proposed Departures from Standards are acceptable, the Departures from Standards will be submitted to the General Manager for final approval. Chapter 2 Geometric Design Manual-2002 Summary of Standards (WKLRSLDQ 5RDGV $XWKRULW\ 3DJH 7DEOH 'HVLJQ 6WDQGDUGV YV 5RDG &ODVVLILFDWLRQ DQG $$'7...
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This note was uploaded on 11/05/2010 for the course CIVIL ce-3020 taught by Professor Era during the Spring '10 term at Trinity College Dublin.

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02 - Chapter-2 - Chapter 2 Geometric Design Manual-2002...

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