Roadways are grouped into functional classes based on the kind of service they are expected to provide. Transportation planners use functional classification to design a safe and efficient flow of traffic throughout the street network. The most basic categories are arterials, collectors, and residential streets.
This system of streets serves the major centers of urban activity and supports the highest traffic volumes. Its purpose is to move people and goods efficiently and quickly, with the highest level of access control.
These streets collect traffic from residential (local) roads and connect them with arterials. Compared to arterial streets, collectors provide a level of service at a lower speed for shorter distances, maintaining a balance between mobility and access.
The great majority of streets in the network are meant to provide the most access to residences and other properties but with a lower level of mobility. These generally interconnect with each other and to collector streets.