[cyberax]

There are no drive-by-wire brakes in the US or Europe for regular cars. Your car's actuator moves the piston that is mechanically linked to your pedal.

So even if the electric system fails completely, you can still actuate the brakes.

[kruador]

Toyota's hybrids, at least, have valves in the hydraulic system. If everything is working, the driver's pedal is isolated from the physical pistons. Pressing the pedal instead moves a 'stroke simulator' (a cylinder with a spring in it), and the pressure is measured with a transducer. The Brake ECU tries to satisfy as much braking demand through regenerative braking as possible, applying the rear brakes to keep balance and front brakes if you brake too hard, requesting more braking than can be generated or the battery can absorb.

If there's a failure of the electrical supply to the brake ECU, or another fault condition occurs, various valves then revert to their normally-open or normally-closed positions to allow hydraulic pressure from the pedal through to the brake cylinders, and isolate the stroke simulator.

Because the engine isn't constantly running and providing a vacuum that can be used to assist with brake force, the system also includes a 'brake accumulator' and pump to boost the brake pressure.

Reference: https://pmmonline.co.uk/technical/blue-prints-insight-into-t...

I don't know for certain, but I would assume that other hybrids and EVs have similar systems to maximise regenerative braking.

[seabrookmx]

It depends on how you define brake by wire, but the one I'm referencing is the C8 Corvette and it's "eBoost" system. This isn't a purely electronic system like throttle by wire is, but it does mean there is no longer a linear relationship between pedal pressure and brake pad pressure. And my point about isolating the driver from feedback still holds true.