Driver & Vehicle attribute problem

[Indigo]

Guys, I have a Batman mesh with a driver attribute and just for fun, I have a Sentinel mesh with vehicle attribute.  Why is it in Rumble Room, I can still control the Sentinel mesh?  Isn't he supposed to be uncontrollable without a driver on it?  And how can I make the Batman mesh ride the Sentinel mesh?

[catwhowalksbyhimself]

The driver/vehicle attributes are not quite yet finished.