In the new Panamera, they do. They are all optional, and expensive, but they range from the basic lane keep assist, as Gunther points out, to full emergency braking, to traffic jam assist, which actually drives the car for you following the car in front up to about 35 mph, to InnoDrive, which looks ahead about 2 miles (using the nav database and real-time traffic info) and sets the car up "for optimum driving under the prevailing conditions", and it will actually steer the car as required. As with other manufacturers, you have to touch the steering wheel as least every ten seconds, or the system will disconnect. We are not far away from an autonomous Porsche.