what defines a road as a blvd., ave., or st.?

Question

I live in LA, and just like anywhere in the US there are roads with their names and suffixes. What qualifies Santa Monica as a boulevard, and Melrose as an avenue? Both run East / West, and both are lined woth businesses for miles.
How are roads assigned their title?

Answer 1

There the same thing.

http://education.yahoo.com/reference/thesaurus/entry/road;_ylt=Ap.URtfkFfxqUXL6tBgkbCuugMMF
road

noun

A course affording passage from one place to another: avenue, boulevard, drive, expressway, freeway, highway, path, roadway, route, street, superhighway, thoroughfare, thruway, turnpike, way.