At the bottom are Local streets and roads. Their primary function is to provide land access. Travel speeds, distances, and volumes are generally low, and through traffic is usually discouraged. Between these extremes are the Collectors whose name describes their function. They collect traffic from the lower facilities and distribute it to the higher.
Collectors provide both mobility and land access.
Generally, trip lengths, speeds, and volumes are moderate. In 1974, the Federal Highway Administration published the manual, Highway Functional Classification - Concepts, Criteria and Procedures . The manual was revised in 1989 and remains the definitive guide to the functional classification process. The manual defines the different functional systems, discusses the general concepts and characteristics used to identify each, and explains the procedures to follow in designating a system. The following discussion is based on this manual.