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Other considerations : various other factors that govern the alignment
are drainage considerations, political factors and monotony.
- Drainage:
- Political: If a foreign territory comes across a straight alignment, we
will have to deviate the alignment around the foreign land.
- Monotony: For a flat terrain it is possible to provide a straight
alignment, but it will be monotonous for driving.
Hence a slight bend may be provided after a few kilometres of straight road to
keep the driver alert by breaking the monotony.
- Hydrological (rainfall/water table):i
Alignment through hilly
areas is slightly different from aligning through a flat terrain.
For the purpose of efficient and safe operation of vehicles through a hilly
terrain special care should be taken while aligning the highway.
Some of the special considerations for highway alignment through a hilly
terrain is discussed below.
- Stability of the slopes: for hilly areas, the road should be aligned
through the side of the hill that is stable.
The common problem with hilly areas is that of landslides.
Excessive cutting and filling for road constructions give way to steepening of
slopes which in turn will affect the stability.
- Hill side drainage: Adequate drainage facility should be provided across
the road.
Attempts should be made to align the roads in such a way where the number of
cross drainage structures required are minimum.
This will reduce the construction cost.
- Special geometric standards: The geometric standards followed in hilly
areas are different from those in flat terrain.
The alignment chosen should enable the ruling gradient to be attained in
minimum of the length, minimizing steep gradient, hairpin bends and needless
rise and fall.
- Ineffective rise and fall : Efforts should be made to keep the
ineffective rise and excessive fall minimum.
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