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We have seen the requirements of an alignment.
But it is not always possible to satisfy all these requirements.
Hence we have to make a judicial choice considering all the factors.
The various factors that control the alignment are as follows:
- Obligatory points:
These are the control points governing the highway alignment.
These points are classified into two categories.
Points through which it should pass and points through which it should not
pass.
Some of the examples are:
- bridge site: The bridge can be located only where the river has straight
and permanent path and also where the abutment and pier can be strongly
founded.
The road approach to the bridge should not be curved and skew crossing should
be avoided as possible.
Thus to locate a bridge the highway alignment may be changed.
- mountain: While the alignment passes through a mountain, the various
alternatives are to either construct a tunnel or to go round the hills.
The suitability of the alternative depends on factors like topography, site
conditions and construction and operation cost.
- intermediate town: The alignment may be slightly deviated to connect an
intermediate town or village nearby.
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