How do you protect yourself from being robbed or hijacked and how often does it occur

Safety in trucking is an issue that comes up often. Usually it is in reference to driving on the highways, truck accidents or driver fatigue.

This concern is about the safety issues in trucking not related to accidents on the highway.

How do drivers handle personal safety? Especially being robbed or hijacked in the truck.

How often does this type of crime happen to drivers?