Why are car roofs not made as hard and stable as possible so that you are no longer killed by trees or light poles?
In: Engineering
Being killed by trees or light poles due to the roof caving in by being hit by one is so rare that the added cost in materials and weight reducing fuel efficiency that a reinforce roof would have is not worth it at all for car makers to design.
Such as design would also raise the center of gravity of the car making it far more likely to roll and thus more dangerous over all.
Not enough cost benefit. Increasing safety features like that would also increase the cost of buying a car and with the ratify of people being killed in cars by falling objects it would be unlikely people would be willing to pay the added cost.
They are made as strong as they can for the price and expected dangers. To make it much stronger would require significant price increases and/or feature reductions. It’s very rare for trees/light poles to land on cars, and car roof have still protected hundreds of people from them. If you want more security look to buy yourself a stronger car.
Because that would make the roof a lot heavier, raising the center of gravity and perhaps making the car more prone to flip. The data shows that the roof not being strong enough is not a huge cause of death in car crashes, therefore it’s cheaper and lighter to make the way it is now.
Because the chance for that to happen is *really* low and making the roofs much stronger will add weight to the car, decreasing fuel efficiency, increasing required stopping distance, adding more potential energy (due to higher weight *presumably* moving at the same speed) to auto accidents, etc.
Cars now have extremely tough roofs. You’ve now prevented an extremely rare freak way people die in cars. In exchange:
* cars are now more expensive due to the extra materials used building the tougher roof
* cars are now more expensive due to increased shipping costs of shipping heavier cars (due to tougher roof)
* cars now have worse gas mileage and increased fuel costs (due to heavier tougher roof)
* cars now wear out their brakes faster and require more frequent pad changes (due to heavier tougher roof)
* cars now have increased stopping distance, increasing the frequency and vehicle speed of accidents.
* cars now have a higher centre of gravity and are more likely to flip/roll in crashes.
The last two points re:safety would probably be enough to completely cancel out the safety benefits of a thicker roof, since that only helps in really specific and rare cases like a tree falling on an occupied car. So now cars are more expensive in at least 4 different ways, for a tiny safety benefit or likely even none at all.
Roofs are designed to hold a lot of weight, in the form of snow for example. But not designed to hold a lot of weight at a single point. A tree hitting the roof focuses all the kinetic energy to one point, whereas the snow can weight the same but be spread out.
Engineering is often intended to achieve a desired result with the minimum material to save on cost. Making a house tree proof would dramatically increase the materials and build costs.
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