on "many" cars? those "many" cars must have been fords 

mazdadan said:I understand the inner workings of car door lock mechanisms as I have dealt with them on numerous occasions. I never said that a car door works like a "dead bolt" on a house. Certain impacts cause the lock mechanism rods inside the door to bend, causing the door to pop open. Granted, on many cars, it doesn't matter if the door is locked or unlocked because the handle inside will still unlock the door. But on all Mazdas with the exception of the pickup trucks, you have to unlock the door before the handle inside the vehicle will open the door. So it technically speaking it is SLIGHTLY safer to have your doors locked.