Grade separated intersection - Definition & Advantage & Disadvantage

Grade separation is the method of aligning a junction of two or more surface transport axes at different heights so that they will not disrupt the traffic flow on other transit routes when they cross each other. 

The composition of such transport axes do not have to be uniform; it can consist of a mixture of roads, footpaths, railways, canals, or airport runways. Bridges, tunnels, or a combination of both can be built at a junction to achieve the needed grade separation.

Advantages:

Roads with grade separation generally allow traffic to move freely, with fewer interruptions, and at higher overall speeds, this is why speed limits are typically higher for grade-separated roads. Also, less trouble between traffic movements reduces the risk of accidents.

Disadvantages:         

Grade-separated road junctions are typically space-intensive, complicated, and costly, due to the need for large physical structures such as tunnels, ramps, and bridges. Their height can be obtrusive, and this combined with the large traffic volumes that grade-separated roads attract, tends to make them unpopular to nearby landowners and residents. For these reasons, proposals for new grade-separated roads can receive significant public opposition.