The information presented in this section is based on Grade-Separated Interchanges: A Design Guide, prepared by the National Association of Australian State Road Authorities (NAASRA), 1984. NAASRA has since become AustRoads, which is somewhat analogous to AASHTO. An interchange, as it is defined in the NAASRA publication, is a combination of ramps and grade separations at the intersection or junction of two roads that is designed to eliminate at-grade turning and crossing movements on the major road carriageways. Interchanges on freeways are the only locations at which traffic can exit from or enter the through route. They should allow for the most efficient and convenient choice of route for the major traffic movements. Interchanges separate major crossing and turning movements and enable maximum traffic volumes to operate safely. Crossing conflicts are reduced or eliminated, and turning conflicts are minimized.