I was involved in a rear-end collision caused by a vehicle abruptly moving into my lane while traveling at a slower speed. From the time the vehicle entered my lane to the time of the collision was approximately one second. Despite this timeframe, the anti-collision warning system and automatic emergency braking (AEB) functionality in my Ford vehicle did not activate or alert me before the impact. Additionally, I have observed that the adaptive cruise control and Blue Cruise systems in my vehicle do not react until a vehicle in front is fully out of the lane (for acceleration) or fully in the lane (for deceleration). This delayed reaction may have contributed to the systems failure to engage in this incident. I believe this represents a potentially unsafe functionality in the collision avoidance system, as it may not adequately respond to rapidly changing traffic conditions. I am reporting this to ensure it is investigated to help improve the safety of these systems and prevent similar incidents in the future.