TABLE OF CONTENTS Once a route has been selected for a new highway, or a decision has been made to perform major work on an existing facility, the next step is to establish the design controls. The various factors considered for design controls may be generally grouped into five categories: functional classification, traffic data, terrain, locale, and design speed.
Functional classification is a way of grouping roadways together by the character of service they provide. The initial division is between urban and rural roadways. The urban classification may be defined differently in various parts of the country, but one definition is incorporated areas having a population of 5000 or more (Ref. 15). Rural areas are those areas outside of urban areas.
Each of these may be further subdivided into other classifications defined as follows:
Interstate. Roadways on the federal system with the highest design speeds and the highest design standards.
Freeway. An expressway with full access control and no at-grade intersections.
Expressway. A divided arterial highway with full or partial control of access and generally having grade separations at major intersections.
Arterial. A facility primarily used for through traffic, usually on a continuous route.
Collector. An intermediate roadway system which connects arterials with the local road or street systems.
Local road or street. A road whose primary function is to provide access to residences, businesses, or other abutting properties.
Traffic data are an important foundation in highway...
