On the following maps, the signs on the different maps are as follows: Red circles which actually say '70' on them are ramps which will enter a slow motion cut scene when gone over at lots of speed. Little white squares that are only just visible are packages. Get 10,20,30,40 and so on and you get weapons for different amounts. Skulls, if you can see them they look like small yellow circles, indicate rampages. These include: Mafia Masacre, Diablo Destruction, Triad Torture etc.
Portland View.
Staunton Island.
Shoreside Vale.