Zone - Vehicle routing

when the vehicles depot build new truck/excavators. there is an option for the zone to be assigned however, i noticed. the vehicle is not being dispatched to the proper zone if it is outside the zone by itself. i have to manually move it then it will work as expected.
it would be interesting if the vehicle which is outside the zone and a zone is assigned to the said vehicle. the vehicle would move to the assigned zone automatically and start it's work instead of manually moving it to the proper zone