. INTERSECTION DESIGN

An intersection is defined as an area where two or more roadways join or cross. Each roadway extending from the intersection is referred to as a leg. The intersection of two roadways has four legs. When one roadway ends at the intersection with another roadway, a three-leg intersection, or T intersection, is formed. Some intersections have more than four legs, but this design should be avoided, since the operation of traffic movements
is usually inefficient. There are three general types of intersections: (1) at-grade, where two or more roadways cross in the same vertical plane, (2) grade-separated, where one roadway is bridged over or tunneled under the other roadway but no turning movements are allowed, and (3) interchanges, a special type of grade-separated intersection where turning movements are accommodated by ramps connecting the two roadways.