Chapter 2: Basic Design Criteria

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Section 1: Functional Classifications

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Overview

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 as either urban or rural. The hierarchy of the functional highway system within either the urban or rural area consists of the following:

  • Principal arterial - main movement (high mobility, limited access)
  • Minor arterial - interconnects principal arterials (moderate mobility, limited access)
  • Collectors - connects local roads to arterials (moderate mobility, moderate access)
  • Local roads and streets - permits access to abutting land (high access, limited mobility)
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