Section 2: Functional Classifications

Anchor: #i1085389


The first step in the design process is to define the function that the facility is to serve. The two major considerations in functionally classifying a roadway are access and mobility. Access and mobility are inversely related - that is, as access is increased, mobility is decreased. Roadways are functionally classified first and then contextually classified as either urban, suburban, or rural. The hierarchy of the functional highway system within either the urban, suburban, or rural area consists of the following:

    Anchor: #AYKOJEJQ
  • Freeways – controlled access facilities (Interstate, Freeways, and Expressways);
  • Anchor: #YUMPWFDF
  • Principal arterial – main movement (high mobility, limited access);
  • Anchor: #IPHSMDKX
  • Minor arterial – interconnects principal arterials (moderate mobility, limited access);
  • Anchor: #VFGWTGMA
  • Collectors – connects local roads to arterials (moderate mobility, moderate access); and
  • Anchor: #OMVLICRY
  • Local roads and streets – permits access to abutting land (high access, limited mobility).

The functional classification of roadways can be viewed on the Statewide Planning Map that is maintained by TxDOT's Transportation Planning and Programming (TPP) Division. The Statewide Planning Map, however, makes the appropriate distinction that freeways are in fact principal arterials. For purposes of design, freeways have unique geometric criteria that demand a separate design designation apart from other arterials.

Previous page  Next page   Title page