Tell me about the various road types in USA?

The public road system in United States of America is primarily made up of Highways and Local Roads. The United States Department of Transportation's Federal Highway Administration (FWHA) classifies roads based on functions which are created based on attributes such as speed limits, route length and spacing. Based on the road functions we can categorize roads into the following categories.
1. Interstates and Arterial System
2. Other Arterials
3. Collectors
4. Locals

The interstate system is the at the top of road function classification system. They include Highways and Freeways with the highest speed limits and which allow for long distance travel without a lot of interruption. They are constructed using precise standards, signage and with safety considerations. They are also sometimes referred to as Arterial roads as they provide vital connectivity across regions in America. Interstate 95 or I-95 is an example of one such highway in the east coast of the United States which runs from Florida to Maine. The Principal Arterial system also comprises of U.S. Highways, which provide connectivity across regions which do not have an Interstate to support travel.

Other Arterials also include freeways and highways which supplement the Interstate system explained above. They have a slightly lesser speed limits. They typically connect cities and urban areas. Consider them as being minor highways. As an example, North Carolina Highway 55 (NC-55) is a primary state highway artery connecting multiple regional and urban areas in the state of North Carolina.

Collectors are critical for connecting urban population using local roads with the Interstate highways where applicable. They have more interruptions and are shorter in lengths. They also have lesser speed limits (30-35 mph). These can comprise of State highways which connect local roads with the Arterial highways.

Finally local roads provide connectivity between communities, regions, farms and other local areas. They form the lion's share of the United States road system.