2010 Toyota Prius Owners Manual - Page 261
2010 Toyota Prius Manual
Page 261 highlights
2 -4 . U sing ot he r driving syst e m s LK A (La ne -Ke e ping Assist ) ∗ While driving on a freeway or motor highway that has lane markings, this system recognizes the lanes using a camera as a sensor to assist the driver with staying in the lane. The LKA system has two functions.