The Tesla Autosteer (equivalent of adaptive cruise control) failed to brake on seeing the car ahead braking. In the 5 seconds before impact, the car ahead had started braking. The autosteer did not brake for the first 3 seconds and then It asked me to take over 2 seconds before collision. It did not apply automatic emergency braking causing me to rear end the car ahead of me on the freeway at around 30mph This is supposed to be a safety driver assist feature which instead was the primary cause of the accident. The take control was too late to avoid collision. This is a serious safety issue.