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Intersections are classified depending upon the treatment of crossing conflicts
as follows
(i) At Grade Intersection and
(ii) Grade Separated Intersection.
It is a bridge that eliminates crossing conflicts at intersections by vertical
separation of roadways in space.
Grade separated intersection are otherwise known as Interchanges.
Grade separated intersections cause less hazard and delay than grade
intersections.
Route transfer at grade separations is accommodated by interchange facilities
consisting of ramps.
Interchange ramps are classified as Direct, Semi-Direct and Indirect.
Interchanges are described by the patterns of the various turning roadways or
ramps.
The interchange configurations are designed in such a way to accommodate
economically the traffic requirements of flow, operation on the crossing
facilities, physical requirements of the topography, adjoining land use, type
of controls, right-of-way and direction of movements.
The ultimate objective of grade separated intersections is to eliminate all
grade crossing conflicts and to accommodate other intersecting maneuvers by
merging, diverging and weaving at low relative speed.
The relative speed of the conflicting vehicle streams is an important factor
affecting the significance of a conflict.
The benefit of providing for low relative speed is twofold.
First, events unfold more slowly allowing more judgement time and second, in
case of an impact the total relative energy to be absorbed are less and hence,
the damage is less.
In addition, when relative speed is low, the average motorist will accept a
smaller time gap space between successive vehicles to complete his move.
This condition increases roadway capacity.
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