[dfox]

The reasoning behind the auto-locking feature is that when the doors are locked it adds to rigidity of the car and thus decreases the likelyhood of the passanger cabin collapsing on the occupants. Auto unlocking the doors would completely defeat the reason for that feature.

The actual mechanism of how the door works as kind of "configurable deformation zone" usually involves somewhat thick steel rod running down the middle of the door that on hinge side abbuts similar strength member in the chasis and on the latch side connects to the latch. The latch has two distinct positions depending on whether the door is just latched or locked and the only latched position is not strong enough to hold the potential impact forces..

[alwa]

Huh! Autolocking behavior has bothered me for as long as I remember seeing it, and I’d love to believe that it improves safety against crashes (rather than notional “bad guys trying to open the door on your journey” or something). It’s only ever inconvenienced me, never helped.

I’m having trouble finding more formal explanations for what you’re describing, though. I see a lot of talk about how the latching behavior links the door’s steel into the rest of the body, but very little about the structural aspects of the locks that link the handles to the latch’s release mechanism.

I’m the farthest thing from a car engineer, but I wonder if you’d know of anyplace I could read more about this structural aspect of locking design? Every time I accidentally lock out a passenger, I get frustrated: I’d find grace and patience easier to muster if I understood how someday it might save both our lives :)

[542354234235]

I am also not a car engineer, but from my reading of "Federal Motor Vehicle Safety Standards; Door Locks and Door Retention Components" [1] it is the latching that is meant to prevent the door opening, not the locks. However, even many modern cars have a mechanical linkage from the handle to the door. In a crash the mechanical linkage, particularly older style tension-type linkages, could unlatch the door when your body hit the door from the inside and physically moved the linkage [2]. A lot of doors use electric actuators now [3], and linkages are much better designed, but it seems like it could still be an issue, in theory.

[1] https://www.federalregister.gov/documents/2007/02/06/07-517/...

[2] http://www.autosafetyexpert.com/defect_doorlatch.php

[3] https://bestsellingcarsblog.com/2023/10/media-post-actuator-...

[burnt-resistor]

> The reasoning behind the auto-locking feature is that when the doors are locked it adds to rigidity of the car

No, this is not the primary reason. The primary reason is safety from potential attack while in a confined, transitional space.

My late grandparents' Lincoln Mark VII non-LSC had autolocking doors when shifting into drive in 1988.