In every car I've ever seen, if you don't close the door with sufficient force, the door gets into a weird semi-closed state. This state is invisible, which is why cars have various indicators and sounds to indicate it. But the lock mechanism is already in force, so in order to properly close it you need to open and close again, unlocking it (which is especially burdensome in case it's child-locked).

Is there a usability reason for this?

Is this just a mechanical limitation, and if so, why is it so hard to solve?

up vote 5 down vote accepted

This almost-locked state is certainly not user friendly when you're not driving.

However, when you're in an accident that causes the car to flip over a couple of times, it may cause the first door lock state to fail. If there was no second lock state, you would fall out of the car while it's spinning.

In short: the semi-closed state is a backup safety feature.

  • 1
    Backup safety trumps usability, I guess... Is there actual regulation for that? – Jonathan May 16 '16 at 7:39
  • @Jonathan I've tried to find data on that, but a fairly quick search didn't bring anything up about the regulations. I can imagine most countries would have regulations about it, especially if almost every car in the world has the same double close state. BTW, some Mercedes cars automatically close the door completely when it's in the semi-close state. So maybe the future looks bright when it comes to closing car doors! ;-) – Max de Mooij May 16 '16 at 23:15

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