The optional PARKTRONIC system makes parking a breeze, however tight the parking space. The system emits ultrasonic signals which are reflected by any obstacles in the path of the C-Class Estate. Displays show you how close the vehicle is to a detected obstacle. Depending on the distance, PARKTRONIC provides a visual signal in yellow or red. It also warns the driver with an intermittent tone if the gap falls below a certain limit. As soon as the gap is less than 20 centimetres, the intermittent tone becomes a continuous tone.