RE: A sombre Introduction
Our Z4 has an electric parking brake. I don't like it.
I've researched how the BMW one works.
If you pull up the brake switch while the car is moving it commands the computer to perform a panic stop. The brake lights come on and the ABS pump applies the service brakes. If there is a failure of the ABS pump, it would do nothing. The service brake should still work even if the ABS pump has failed. Power assist is separate from the ABS pump.
The BMW system has substantial fault tolerance. For most failures, something would still work.
When the car isn't moving the park brake uses electric motors to apply the rear brakes. -- One of the biggest problems is if the battery master fuse goes when the parking brake is applied. No way to release the brake. The battery is in the boot and the boot release is electric!