In an interview with TechCrunch’s Brian Heater, Apple’s vice president of Sensing & Connectivity, Ron Huang, and vice president of Worldwide iPhone Product Marketing, Kaiann Drance explain how the iPhone 14 and 14 Pro and Apple Watch Series 8 and Ultra detect car crashes. A big part of the equation is the new gyroscopes and accelerometers the devices use. The accelerometers measure G Force, while the gyroscopes detect speed changes. Other sensors come into play, too, including the barometer, GPS, and microphone, as well as Bluetooth and CarPlay.

Not every sensor needs to be triggered to detect a crash, although multiple data points are necessary. As Huang explained:

There’s no silver bullet, in terms of activating crash detection. It’s hard to say how many of these things have to trigger, because it’s not a straight equation. Depending how fast the traveling speed was earlier, determines what signals we have to see later on, as well. Your speed change, combined with the impact force, combined with the pressure change, combined with the sound level, it’s all a pretty dynamic algorithm.

The system will also try to make calls to emergency services first using your mobile provider and will fall back to any other networks as necessary. The crash detection feature will be connected to Apple’s upcoming satellite service when it becomes available to handle the situation where no mobile network is available too.

For more details on how crashes are detected and the testing that went into developing the feature, be sure to read Brian Heater’s story. Also, it’s worth noting that TechCrunch’s interviews appear to have been done before recent reports emerged of roller coasters setting off the crash detection feature.