The windows in a car are constructed to exact specifications, but the needs of these windows differ depending on where they are located in the car.

Whilst the windscreen needs to be strong enough to stay in one piece even when shattered before it is repaired or replaced, the back windows are often designed to be strong but ultimately break in the event of an accident.

Both are made from different types of glass; windscreens are made from laminated glass whilst other car windows are typically made from some form of tempered glass.

Laminated glass is made from two or more layers of glass sandwiched between a sticky plastic layer. When it breaks, rather than fracturing into sharp shards that can cause lacerations, it maintains its shape and some of its structural rigidity, helping to protect people in accidents.

Whilst it is illegal to drive with a windscreen cracked enough to harm visibility, it is a much safer option than one that is allowed to break and shatter.

By contrast, other car windows are made from tempered glass, a safety glass that works by using heat or chemical reactions to create sheets of glass that have a mix of different stresses that create an equilibrium.

The result is glass that is significantly stronger than standard sheet glass but is designed to shatter into a lot of smaller, safer chunks rather than shards. It can also be broken if the car rolls over, allowing people to get out more quickly.

This has led to some controversy in recent years regarding the driver and front passenger side windows, which can sometimes be made of laminated glass to avoid the risk of a driver being thrown from the vehicle in the event of a rollover.

It can also make the car quieter, so it has increasingly been added as an optional extra or a feature on luxury cars, so it is important to keep that in mind if they need replacing.