2012 Toyota Prius Owners Manual - Page 1101

2-4. Using other driving systems Driving in vehicle-to-vehicle distance control mode This mode employs a radar sensor to detect the presence of vehicles up to approximately 400 ft. (120 m) ahead, determines the current vehicle-to-vehicle following distance, and operates to maintain a suitable following distance from the vehicle ahead. Note that vehicle-to-vehicle distance will close in when traveling on long downhill slopes. 240 PRIUS v_U (OM47784U)