Grade Separated Intersection
The road intersections where all the roads join or cross at a different level by providing a bridge (over bridge or underpass), is called grade-separated intersection.
Classification of Grade Separated Intersection
The various grade separated intersection are classified into the following two categories.
When the major Highway is taken above by rising its profile above the general ground level by an embankment and an overbridge across another highway, it is called an overpass. Cloverleaf pattern fly-over, trumpet-type fly-over is the example of overpasses.
When the highway is taken by it depressing it below the ground level to cross another road by means of another bridge, it is called an underpass.
Advantages of Grade Separator
The advantages of providing grade separator are as follows:
⇛ Grade separator provides maximum facility to the crossing traffic and avoids the accident while crossing.
⇛They provide increased safety for turning traffic. By introducing indirect interchange ramp, even right turn movements can be made quite easy and safe.
⇛ Grade separation is an essential part of controlled access highway like an expressway.
⇛ It is possible to adopt grade separation for all likely angles and layout of intersecting roads.
⇛ Stage construction of additional ramps is possible after the grade separation structure between main roads is construction.
⇛ Traffic capacity is increased.
Disadvantages of Grade Separator
The disadvantages of providing grade separator are as follows:
⇛ The construction cost is very high.
⇛ Construction of grade separator is costly, difficult and undesirable where there is limited right of way or where the topography is not favourable.
⇛ In flat or plain terrains, grade separation may introduce undesirable crests and sags in the vertical alignment.