It works by radar and camera. The first stage is showing an alert. Second stage is preparing the brakes. If you hit the brakes it will apply more brake pressure as normal. The third stage is auto braking.
Please note that it will try to minimise the crash, it will not always prevent it. Also as soon as you touch the brakes the system wil not do anything any more because the system assumes you are reacting.
Please note that it will try to minimise the crash, it will not always prevent it. Also as soon as you touch the brakes the system wil not do anything any more because the system assumes you are reacting.