The ability to accommodate high volumes of traffic safely and efficiently through intersections depends largely on the arrangement of the intersection. Grade separations offer the greatest efficiency, safety, and capacity for intersecting roadways.

The decision to provide a fully access-controlled facility becomes the warrant for providing highway grade separations or interchanges at the most important intersecting roadways (usually arterials and some collectors) and railroads.

An interchange or series of interchanges on a freeway through a community may affect large continuous areas or even the entire community. For this reason, interchanges must be located and designed so that they will provide the best possible traffic service. Drivers who have exited from a freeway expect to be able to re-enter in the same vicinity; therefore, partial interchanges that do not serve all desired traffic movements should be avoided.

For information on the design of Diverging Diamond Interchanges, see .