Windshields need to be made from strong laminated glass. In previous years the windshields of vehicles were made from ordinary house glass but this proved to be dangerous especially if the windshield broke. If the windshield of a vehicle that is made from ordinary house glass similar to the glass used to make cups it would be extremely dangerous for the passengers within the vehicle. House glass shatters very easily and when it does each piece is incredibly sharp; it can be so sharp that you do even realize that you have been cut after awhile. So in other words house glass is very dangerous and it is not a good idea to use house glass for windshields. Modern windshields use a special type of glass that will not shatter very easily and when it does the shards of glass will not be as dangerous as house glass. So if a large rock collides with a windshield that is made from house glass the windshield will shatter sending shards everywhere. However if a rock collides with a modern day windshield the windshield absorb most of the damage and unless the rock is thrown with a incredible force it will not go through the glass.