I'll take a stab at "free air"...
The best street definition I can come up with is an installation as the utility companies use. Single conductors mounted on cross arms or similar approved methods on poles. I could take it a step further and mention the "older" rack service drops at some commercial buildings; a "rack" is mounted to the exterior wall, on which insulators are mounted, and individual conductors are mounted to the insulators. This is not a commonly used installation now.
Hope this helps