It depends on what type of car,model, and year. If it is a more modern car then it should have child safety locks which is a little thing on the door that you slide, lock or unlock. This is in a place where kids will not be able access it. Having kids myself and always keeping themsafe, its a never ending job, at least we can rest easy while in the car. Four door cars are easier with children as well, trying to get them into two door cars and then trying to get us back there to make sure they are buckled and safe. So a four door car as long as its an up to date modern car with child safety locks.