In the 1960s, as interest in auto safety grew, engineers began researching various headlamp cleaning systems. In late 1968, Chevrolet introduced high pressure fluid headlamp washers on a variety of their 1969 models. In 1970, Saab Automobile introduced headlight wipers across their product range. These operated on a horizontal reciprocating mechanism, with a single motor. They were later superseded by a radial spindle action wiper mechanism, with individual motors on each headlamp. In 1972, headlamp cleaning systems became mandatory in Sweden. Headlamp wipers have all but disappeared today with most modern designs relying solely on pressurized fluid spray to clean the headlights. This reduces manufacturing cost, minimizes aerodynamic drag, and complies with EU regulations limiting headlamp wiper use to glass-lensed units only (the majority of lenses today are made of plastic.)