What is an Road Intersection?
Road Intersection is where two or more roads meet and or are the points of potential vehicle conflict. They are critical element of a road section. They are normally a major bottleneck to smooth flow of traffic and a major accident spot. The general principles of design in both rural and urban areas are the same. The dangers to pedestrians and riders of two-wheeled vehicles are also great at intersections.
Grade separation is a form of intersection in which one or more conflicting movements of intersecting highways are segregated in space. An interchange is a grade separation with connecting roadways which allow route transfer between the intersecting highways. An interchange is therefore, the highest form of intersection design. The type of interchange, the shape and pattern of the interchange ramps for the various turning movements, and their design are governed by several factors such as the importance of the intersecting highways, the number of intersecting legs, the design volumes of through and turning traffic movements including their composition, the design speeds, available right of way and topography. Interchanges, therefore, are necessarily designed individually in light of the above considerations.
Type of intersections and Choice
From a design aspect, intersections can also be divided according to whether they are uncontrolled, priority (stop give way), space sharing (round about), time-sharing (traffic signal controlled), or grade separated (interchanges). The four categories given in IRC code (special publication, 1994) are:
Uncontrolled at-grade: These are the intersections between any two roads with relatively lower volume of traffic and traffic of neither road has precedence over the other.
Priority control: There is theoretically no delay occurring on the major road and vehicles on the minor road are controlled by “GIVE WAY” or “STOP” signs.
Time separated /Signalized intersection at grade: These are widely seen road intersection with traffic signals.
Space separated/Grade separated intersection: These intersections facilitates movement at different levels for vehicles and pedestrians. Example of such type include intersections with flyovers, under pass
Road intersection types based on geometric:
- T
- Y
- Scissor
- Cross
- Staggered
- Staggered and Skewed
- Multiway
The intersections can therefore be divided into different types on the basis of their geometric design. Figure below illustrates the same.
Read about: Design principle for intersection, Level of Service
