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The position or the layout of the central line of the highway on the ground is
called the alignment.
Horizontal alignment includes straight and curved paths.
Vertical alignment includes level and gradients.
Alignment decision is important because a bad alignment will enhance the
construction, maintenance and vehicle operating costs.
Once an alignment is fixed and constructed, it is not easy to change it due to
increase in cost of adjoining land and construction of costly structures by the
roadside.
The requirements of an ideal alignment are
- The alignment between two terminal stations should be short and as far as
possible be straight, but due to some practical considerations deviations may
be needed.
- The alignment should be easy to construct and maintain.
It should be easy for the operation of vehicles. So to the maximum extend easy
gradients and curves should be provided.
- It should be safe both from the construction and operating point of view
especially at slopes, embankments, and cutting. It should have safe geometric
features.
- The alignment should be economical and it can be considered so only when
the initial cost, maintenance cost, and operating cost are minimum.
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