The rating system: 1/5 - Not very good. 5/5 - Best on the map. There will be a combination of these variables throughout. For example, some spots are great for cover and safety but are not very good for getting kills; rather they are good for countering certain camping spots.
Traffic refers to how long you'll have to wait before enemies appear. Higher traffic areas are usually less safe. But when both variables are high, the spot is very good. 1 or 2 level safety spots should be moved out of or only moved through due to the possibility of being spawned on.
Vol 1
Vol 2
Feedback is welcome. I'm still working out some other spots I have found.