For a general no-go area:
Create a trigger where U want your boundary (make a long small ellips)
-Detected by anybody
-In the Condition field:vehicle player in thislist
-In the on-activation:?(vehicle Player in thisList) then { Titletext[format["WARNING whatever"],"Plain down"]
U can add more commands,like and playsound "alarm" and player setdammage 0.5.....