GSX vehicles are not entirely aware of each other. If we tried doing this, it would slow down performances a lot (since every vehicle should monitor all the others), and it would probably open to an entirely new class of problems, like traffic deadlocks on the apron and who's supposed to yeld to whom.
But you can fix most of the issues, by setting a different starting position for them, which is the main reason of being allowed to customize the starting position for each vehicle.