I don't know how the law in your state is, but in Michigan, if we are stopped, and carrying, we are required by law to notify the officer...in Michigan (as in some other states) when you are in a vehicle, your pistol is considered to be concealed, and you better have a permit.
Consequently, the few times I've been stopped by police while driving, I always inform, up front, and hand over my CPL (Concealed Pistol License) along with my drivers license and proof of insurance, and of course, I tell them I'm packing and where it is. So far, no problems, and interestingly enough, no tickets either.
In Oregon you don't have to tell the police that you are carrying concealed; in fact, some carry gurus think you shouldn't, as it scares them. (This is different in other states I've been in--Utah, Ohio, and North Carolina.) The cop in the infamous incident I mentioned was unaware of this. In a vehicle, it depends on whether it is in plain sight or not. I heard of one man who was stopped by a cop and his gun slipped under the seat coincidentally. He was busted for carrying concealed. However, due to budget cuts, the county DA where I live is not prosecuting dips__t crimes like that. On another point: I once had to drive into California and didn't want to have the hassle of putting my gun away. I now know that if it were a revolver, I could carry it open, if unloaded, with a speed loader in pocket. You can load a revolver almost as fast as you can draw it. Or you can simply say to your assailant: