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Comment by puffoflogic | Hacker News Reader

Sometimes the engineers are "too" clever. In my car, seatbelts have an additional mechanism which causes them to stop if the car is braking (with a certain acceleration, perhaps, or actual detection of the brake - I haven't determined). This seems very sensible until you live near an intersection which is not at right angles, which requires the driver to lean forward upon arrival at the intersection in order to look around the A pillar for oncoming traffic.

What's interesting is that I now know something that the engineers designing the system should have known but apparently didn't, or knew and didn't care about. So sometimes (or much of the time?) users do know something the engineers don't.

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> In my car, seatbelts have an additional mechanism which causes them to stop if the car is braking (with a certain acceleration, perhaps, or actual detection of the brake - I haven't determined). This seems very sensible until you live near an intersection which is not at right angles, which requires the driver to lean forward upon arrival at the intersection in order to look around the A pillar for oncoming traffic.

This is a tradeoff.

You can have a pure pay-out based locking retractor (centrifugal clutch). Or you can have a pendulum-based mechanism, or a combination of the two.

If you have the pendulum-based one, you'll be less likely to false positive based on the movement of the occupant but more likely to false positive based on deceleration of the vehicle.

The combination is best, because you can be relatively insensitive to individually occupant movement and vehicle deceleration and still actuate reliably in a crash. But it still will false positive.

In any case, "not annoying the user" is prioritized beneath "saving lives in a crash" by regulators, and hence the auto industry.

I'm guessing you brake rather abruptly in this situation if this is something you routinely encounter.

I recently upgraded vehicles from a 2009 to a current one with all the new safety features. In my research I read lots of complaints about emergency/auto braking activating too much and other features of the car stepping in to assist the driver. Since switching vehicles, on the incredibly rare occasions something has activated, it's always been valid and a quicker reaction than my own.

Your tag line reminds me of all the times I've pondered how bad these complaining drivers must be.

Odd that you should mention this: tonight my car decided it needed to ABS brake (very alarming when unexpected) while I was reversing at less than 5 mph, apparently because a car >20 feet away was turning into a parking spot, well out of my path of travel. The car proudly informed me it had averted a collision, when in fact the application of the brake was unnecessarily violent enough that it quite possibly did damage on its own, and could have caused injury. Progress!

This is one of the things I love about open source software. When I want or need to, I can attempt to modify something to better suit the behavior I want. Some fraction of the time it ends up being too much effort, or I learn that my idea didn't take into account some secondary factor. But often enough I make can make a change, and even maybe contribute it back. I'd love to see more open-source with physical product - 3D printing seems like a good start.

I think the auto-locking is pendulum-based. I've noticed that on steep slopes the seatbelt tends to lock very easily.

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