Most cars (all?) with automatic transmissions have some physical button somewhere--usually hidden--that is a "parking lockout over-ride" feature.
For example, in the Toyotas (multiple) I used to drive, the button was hidden under a small piece of black plastic near the shift lever itself. You had to pry off the plastic cover, then you could push the button to allow you to change into Neutral.
EDIT: Wow, what dumb luck. Just looked up and saw PTinVT essentially said the same thing as me.
To an imperial city, nothing is inconsistent which is expedient.
--Thucydides, 420 BC