An automated collision mitigation system of a vehicle includes a vehicle controller, a free space monitor unit, a rear collision monitor unit, a communicator, a drivetrain system and a braking system. The free space monitor unit detects a free space in front of a host vehicle and the rear collision monitor unit detect parameters of a remote vehicle located rearwardly of the host vehicle. The communicator sends and receives signal from the other vehicles or infrastructures by V2V or V2I wireless network. The vehicle controller evaluates an accelerating time of the host vehicle and a time-to-collision of the rear remote vehicle. In addition, the vehicle controller determines to activate the drivetrain system or the braking system of the host vehicle.