The windshield or windscreen of an aircraft, automobile, bus, motorcycle, or tram is the front window. Modern windshields are generally made of laminated safety glass, a type of treated glass, which consists of two (typically) curved sheets of glass with a plastic layer laminated between them for safety, and are glued into the window frame.

Motorcycle windshields are often made of high-impact acrylic plastic. As the name implies, their main function is to shield the driver from the wind, though they do not do so as totally as those of a car.

Usage

In daily use, windshields mainly protect the vehicle's occupants from wind, temperature extremes, and flying debris such as dust, insects, and rocks, as well as providing an aerodynamically formed window towards the front. UV Coating may be applied to screen out harmful ultraviolet light.

Safety

Early windshields were made of ordinary window glass, but that could lead to serious injuries in the event of a crash. They were replaced with windshields made of toughened glass and were fitted in the frame using a rubber or neoprene seal. The hardened glass shattered into many mostly harmless fragments when the windshield broke. These windshields, however, could shatter from a simple stone chip. In 1919, Henry Ford solved the problem of flying debris by using a new technology founded in France called glass laminating. Windshields made using this process were actually two layers of glass with a cellulose inner layer. This inner layer held the glass together when it fractured. Between 1919 and 1929, Ford ordered the use of laminated glass on all of his vehicles.

The modern, glued-in glass contribute to the vehicle's rigidity, but the main force in innovating the windshield has historically been the need to prevent injury from sharp glass fragments. Modern windshields, now almost universally required in all nations, do not fragment, but tend to stay in one piece even if broken, except if pierced locally by a strong force. Properly installed automobile windshields are also essential to safety; along with the roof of the car, they provide protection in the case of a roll-over accident in the vehicle.

Other aspects

In many places, laws restrict the use of heavily tinted glass in vehicle windshields; generally, laws specify the maximum level of tint permitted. Some vehicles have noticeably more tint in the uppermost part of the windshield of motor vehicles that blocks glare from the sun.

In aircraft windshields, a current is applied through a conducting layer of tin(IV) oxide to generate heat to prevent icing. A similar system for automobile windshields, introduced on Ford vehicles as "Quickclear" in Europe ("InstaClear" in North America) in the 1980s, uses very thin heating wires or conductive-film layer embedded between the two laminations.