The purpose of this section is to overview aspects of traffic theory that form the basis of flow management on road facilities. This area of traffic management has been given increased attention by transport professionals since the 1980s, particularly in relation to freeways and other high standard facilities (Akcelik et al. 1999; Brilon 2000; May 1990).
Much of the theory underlying these developing approaches to flow management is not new but draws on the established relationships of traffic flow. However, using different ways of viewing key traffic characteristics, particularly density, researchers and traffic managers have been able to gain new insights into freeway performance and guidance on how that performance can be improved.