Surveying

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					      Highway Location
I.    * Principles of Highway Location
1.    allowing convenient, continuous, free-flowing traffic operation,
      and
2.    best meeting the major traffic desire lines and being as direct
      as possible.
II.   *Highway Location Practice
1.    Keep grades and curvature to the minimum
2.    Avoid sudden changes in sight distance, especially near
      junctions
3.    Avoid having the beginning or end of a sharp horizontal curve
      on or adjacent to a pronounced vertical curve
4.    Site the highway through undeveloped areas in urban areas,
      along the edges of large parklands and away from expensive
      land areas
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                         Highway Location
II.   Highway Location Practice
5.    Seek locations which result in the least amount of
      environmental unfavorable impact (visual and audio) to
      affected householders
6.    In urban areas locate the highway as close as possible to the
      principle parking terminals
7.    In rural areas locate as much as possible of the new highway
      on existing ones, so as to minimize the loss of farmland and
      to reduce the total initial and maintenance costs
8.    Locate the highway along the edges of properties rather
      than through the middle
9.    Avoid the destruction or removal of man-made culture

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                       Highway Location
II.   Highway Location Practice
10.   Keep the highway away from cemeteries, places of worship,
      hospitals, schools and playground
11.   Consider the effect of the proposed highway on existing or
      future utilities above, on or under the ground
12.   Never have two roads intersecting near a bent or at the top
      or bottom of a hill
13.   In the case of a motorway, economically locate an
      interchange at a place, at an angle and in terrain
14.   Avoid intersections at-grade with railway lines , the
      highway passing over the railway at a point where the
      railway goes into a cutting
15.   Seek favorable sites for river crossings at right-angles to
      the stream centerline
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                          Highway Location
II.   Highway Location Practice
16.   Do not have a bridge or tunnel located on or adjacent to a
      highway curve
17.   Avoid the need for deep cuttings and expensive tunnel
      construction
18.   Avoid locations where rock is close to the surface
19.   In hilly terrain reduce the maximum gradient to the lowest
      value possible
20.   To minimize drainage problems, select a location on high
      ground in preference to one in a valley
21.   Avoid bogs, marshes and other low-lying lands subject to
      flooding
22.   Locate the highway on soil which will require the least
      pavement thickness above it
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                          Highway Location
II.   Highway Location Practice
23.   Locate the highway adjacent to sources of construction
      materials, if possible
24.   If possible, the best location is the one which results in the
      minimum total cost of earthworks, i. e., the minimum
      quantities of excavation equals that of embankment as to
      require a minimum of haulage with little need for overhaul
25.   In hilly terrain the highway should cross ridges at their
      lowest points for cheaper construction and more economical
      vehicle operating costs
26.   Avoid creating severe breaks in the natural skyline
27.   In hilly country, select a location subject to sunlight so that
      moisture or snow and ice on the carriageway can evaporate,
      melt and dissipate
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                         Highway Location
II.   Highway Location Practice
28.   Avoid the unnecessary and expensive destruction of wooded
      areas. If intrusion is unavoidable, the road should be on a
      curve, where possible, so as to preserve an unbroken
      background.
29.   Avoid ground subject to subsidence or landslip.
30.   Avoid placing the highway at right-angles to a series of
      natural drainage channels.

III. Homework
    What would be the common practices in highway location?
    What should be paid attention to at intersections for a highway
      location?
                          Highway Location
Sight distance is the length of highway visible ahead to the driver
     of a vehicle.
The three types of sight distance common in roadway design are
     intersection sight distance, stopping sight distance, and
     passing sight distance.

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