Thought about this on my way to a friend's house...a car can only be in 4 driving states: park (P), reverse (r), drive (d) or neutral (n). If we think about this in terms of binary, in park, the car cannot go forward or backward (0, 0), reverse (1,0), drive (0,1) and neutral (1,1) 0 being locked, 1 being unlocked. Also, the car can only be in one of these states at a time. Hope you enjoy the logic.
