Q. My wife insists that we lock the doors when driving so they don't “pop open accidentally.” I prefer unlocked, because should we have an accident, the first one on the scene doesn't have to break a window to get into the car. She thinks we should lock them anyway. What do you think? — Tom
TOM: Well, she's right, Tom, but for the wrong reasons.
RAY: Doors are pretty good at staying closed, even when they're not locked. They're required by federal regulation to resist at least 2,500 pounds of pressure before coming open.
TOM: It's important that doors do stay closed in an accident for three reasons: (1) So you're not ejected from the car, (2) so if you slide into a tree or a telephone pole, the door takes the first hit, rather than your spleen, and (3) so the roof doesn't collapse. The doors are an important part of the car's structural integrity, holding up the roof and keeping the body from twisting.
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RAY: Does locking the door add any further protection to keep the doors closed in an accident? The answer is, sometimes, yes.
TOM: In some severe accidents, the inertia – just the force created by crashing into something – can be enough to move the rod or springs inside the door and allow the door to open.
RAY: And by locking the door, you simply eliminate that possibility.
TOM: I wouldn't be too worried about someone getting to you in an accident. First of all, lots of cars automatically unlock their doors now if the air bag goes off. But even if that doesn't happen, if you're in an accident that's so bad that you're unconscious and unable to unlock the door for a rescuer, someone can always break a window. Replacing a window will be the last thing you'll be worrying about then.
RAY: So lock the doors when you're driving. You'll not only increase your safety in an accident, but you'll also increase your safety around town – by preventing unsavory characters like my brother from getting into your car.