Road classification for planning and design

The concept of road classification is introduced, and the fundamentally important functional classification is discussed in detail. The classical hierarchy, with its grading of roads from an access emphasis at one extreme to a movement emphasis at the other is reviewed, and problems with the application of such a hierarchy in practice are raised. It is argued that a significant drawback with this hierarchy is its explicit assumption that access is a continuous function; instead, access is in reality a discrete function and either exists on a street or does not. Following this argument, it is suggested that an alternative and superior functional classification system is to divide streets into those which provide access and those which do not. Design standards appropriate to roads and streets within each of these categories are suggested.