Wednesday, 29 August 2018

Grade separated intersection and their advantages and disadvantages & classification

Grade Separated Intersection

The road intersections where all the roads join or cross at different level by providing a bridge (over bridge or  under pass), is called grade separated intersection. 
The various grade separated intersection are classified into the following two categories.
1. Over passes 
2. Under passes

Over Passes


when the major Highway is taken above by rising its profile above the general ground level by embankment and an over bridge across another highway, it is called and over-pass.Clover leaf pattern fly-over ,trumpet type fly-over are the example of over-passes.

Under Passes


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 under pass.

Advantage of Grade Separator

The advantages of providing grade separator are as follows:
⇛Grade separator provides maximum facility to the crossing traffic and avoids 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 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.

⇛The traffic capacity is increased.

Disadvantage 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 favorable.

⇛In flat or plain terrains,grade separation may introduce undesirable crests and sags in the vertical alignment.