YES! It will. I have experienced the HUD lights and sound as well as initiation of braking at speeds between 40-50 mph. Since I intervened very quickly, and the situation was essentially a false alarm (car merging out of my lane), the system did not continue to brake hard. Many folks are failing to realize that the ACC option provides this function for high speed automatic braking. For me, ACC's adaptive cruise control function is secondary to the automatic braking sophistication it provides beyond the optical-only sensor that comes with DCP-2.If I am driving 45 MPH or 55 MPH and the car senses I might hit the object in front of me, will the car try to stop itself?