# How does a seatbelt locking mechanism work?

**URL:** <https://boards.straightdope.com/t/how-does-a-seatbelt-locking-mechanism-work/235409>\
**Category:** Factual Questions\
**Created:** [March 20, 2004, 4:29pm UTC](https://boards.straightdope.com/t/how-does-a-seatbelt-locking-mechanism-work/235409 "2004-03-20T16:29:40Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![Vision\_of\_Love](https://avatars.discourse-cdn.com/v4/letter/v/5f8ce5/32.png) [@Vision\_of\_Love](https://boards.straightdope.com/u/Vision_of_Love)\
**Post date:** [March 20, 2004, 4:29pm UTC](https://boards.straightdope.com/t/how-does-a-seatbelt-locking-mechanism-work/235409/1 "2004-03-20T16:29:40Z")

</div>

This is something that has made me wonder since I was a kid, playing with and repeatedly tugging at the seatbelts during car rides.

My question is simple: How does the seatbelt lock at quick jerks and not lock at pulls? Also, even when our car made only a slightly jerky stop, the belt would still lock, even though the belt actually moved rather slowly. Does the belt mechanism receive signals from the car at all?

---

<div class="post-metadata">

**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\
**Post date:** [March 20, 2004, 4:39pm UTC](https://boards.straightdope.com/t/how-does-a-seatbelt-locking-mechanism-work/235409/2 "2004-03-20T16:39:43Z")

</div>

> **[How Seatbelts Work](https://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/seatbelt3.htm)**
>
> Seatbelts save thousands of lives each year. How can a piece of fabric end up being the difference between life and death? What does a seatbelt actually do? Learn how seatbelts react in a crash.