> presumably there's no good way to talk to the built-in system; having a second system running that can't coordinate with the self-driving system would likely

> presumably there's no good way to talk to the built-in system; having a second system running that can't coordinate with the self-driving system would likely make the combined system less safe. Honestly, this is a cop-out. A substantial amount of information is available from the vehicle's CAN networks - including speed and braking action! If the autonomous driving system detects sudden and unplanned changes in speed and/or braking (perhaps caused either by the driver, an external safety system or some kind of impact with something on the road) then the obvious choice there is for the autonomous driving system to release control of the vehicle and let whatever existing systems in the car, or even the driver, handle what is happening. The car's built-in safety systems are a) simpler, b) less likely to malfunction and c) substantially better road-tested. There was no reason whatsoever to disable them.