I had rented an SUV last summer, I think it was either a Ford Explorer or Expedition. It had the steering assist, to help keep the vehicle between the lines. Well, since I was working overnight, I'd be driving on the highway at 3am, and decided to try it out. Had the cruise set, and would take my hands completely off the wheel just to see how it tracked. It wasn't too bad, a little nervous when the road would curve, but if you did not put your hands back on the wheel after 30 seconds, it would turn off the cruise control. Also, if you were approaching an exit where the lane would split, like the link below, it would try to follow the lines to the right, taking you off the highway, when I wanted to stay on.
https://goo.gl/maps/SEw1SKAZcXaPqm9SA