TACC cannot detect all objects and, especially in situations when you are driving over 50 mph, may not brake when a vehicle or object is only partially in the driving lane or when a vehicle you are following moves out of your driving path and a stationary or slow-moving vehicle or object is in front of you. Always pay attention to the road ahead and stay prepared to take immediate corrective action. Depending on TACC to avoid a collision can result in serious injury or death. In addition, TACC may react to vehicles or objects that either do not exist or are not in the lane of travel, causing the car to slow down unnecessarily or inappropriately.
Emphasis mine. Interestingly the verbiage is slightly modified from prior versions.