The runway gets all the glory, but the apron is where the collisions happen. Unlike runways, aprons are "non-movement areas" (or controlled movement areas depending on the airport), often controlled by Ground Control or Apron Control.
According to standard international handbooks (ICAO Annex 14), the apron is a rainbow of meaning. Here is the cheat sheet: Apron Markings Signs Handbook
You cannot simply drive onto the tarmac. To operate on the apron, you must pass a test based on the local (often called the "Ramp Driving Manual"). The runway gets all the glory, but the