I’m thinking specifically about how breakable safety glass is important so that you can escape through a broken window if your car falls into a body of water, or how crumple zones are designed so that it’s the car that gets smooshed, rather than your brain and organs. But official state cars, like Cadillac One/”The Beast,” have bodies that are way stronger/heavier than a normal car and bulletproof glass windows, so how do they protect the occupants if there’s some kind of freak accident?
(I realize that the best plan is to avoid such a situation in the first place, but given that Cadillac One is hermetically sealed to protect against gas attacks and has electrified handles to keep people from getting in, I can’t imagine that no one has ever considered “what happens if the car accidentally ends up in a lake?”)
In: Engineering
I just want to point out, safety glass on cars is not there in case it ends up in the water. Tempered glass is used on the side and rear windows because it is very resistant to blunt force impacts like rocks being kicked up and hitting the glass. In addition when it does break it crumbles into small pieces that don’t have razor sharp edges. This means the broken glass is not likely to do serious harm to an occupant.
Because tempered glass is either whole, or crumbled, it is not used on the front window. Plate glass is used there because it is more important the windshield remain in place than it is to protect it against chipping or cracking if struck by a rock or other small road debris. To protect the occupant they laminate two sheets of glass together and the plastic laminate in the middle prevents someone from going thru the glass and being sliced by razor sharp edges.
With that in mind it changes your entire premise over the potential dangers to using bulletproof glass. The bulletproof glass provides all the same safety features that tempered glass provides. It won’t chip or crack from road debris and since it won’t break at all, you don’t have to worry about it cutting someone. It doesn’t get used in all cars because it is heavier and more expensive and unnecessary. Yes tempered glass makes it easier for EMS to gain access to you in an emergency, but that isn’t really a design consideration, it is just a benefit.
As for other safety features like crumple zones, those are there because the average driver is not very good and it is better to destroy the car than it is to injure the occupants. A high profile secure car is designed to survive accidents and remain mobile so the driver can still drive away. The drivers themselves are highly trained so any crash they get into is very unlikely to be an accident and instead is due to a deliberate attack. In terms of keeping the occupants safe, airbags can still be used in the passenger compartment as well as better seatbelts and interior padding. Also, a properly reinforced frame, with a properly secure passenger, can survive pretty significant accidents with little to no injury. Regular cars aren’t built this way because it adds a huge amount of weight and cost and the safety you gain is quickly lost when you don’t wear your seatbelt correctly and you dump loose bags if groceries behind you providing a pile of projectiles to bounce around inside, and you attach phones to your dashboard, and any number of things people routinely do that means they are no longer securely strapped to a crash cube. Again, car safety features exist the way they do specifically because the average driver is an idiot and doesn’t bother following all proper best practices for safety.
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