Road hierarchy

The hierarchy of roads describes the functions of different types of roads. While sources differ on the exact nomenclature; in general, they describe the same thing.

At the top of the hierarchy are limited access roads or freeways, that serve the purpose of movement from point A to point B, but do not allow direct access to property. These roads have the highest design speeds, and carry the most traffic.

Next are major arterials and minor arterials which connect each other and lower level roads. These roads may or may not allow access, and typically have at-grade intersections controlled by traffic lights.

These are followed by collectors and distributors, which don't have a significant through movement function, but are intended to provide property access, and connect properties to the higher network. These are more likely to be controled by traffic signs.

At the bottom of the hierarchy are local roads. These roads have the lowest speed limit, and carry low volumes of traffic.

Roads have been distinguished by function probably since their beginning, and the hierarchy of roads was firmly established by the time of the Roman Empire.