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I wonder if there is an implicit question being asked -- how can "light" fuel efficient cars be as safe as heavier less fuel efficient cars?
The irony is that many/most of the heavy SUV's that get such horrible fuel mileage are also much less safe either because they are not required to have the same crash tests as "cars", or because they have very high Cg (center of gravity), and/or they take longer to slow/stop *because* they are heavier. The commonly held myth is that it is the weight of a vehicle that makes it safe. If that was true, then why not just make them out of lead or concrete?
The fact is that it is good engineering that makes a vehicle safe, and that in a majority of types of crashes -- higher weight is a huge liability. The only type of crash that being heavier gives an "advantage" is in a head on crash, and only then if the heavier car is well engineered. In *all* other two vehicle crashes and *all one* vehicle crashes, being in a lighter vehicle is a big advantage. A single vehicle that hits some sort of external object like a tree or a bridge abutment has a given amount of kinetic energy that it has to absorb -- that is *directly* proportional to the weight of the vehicle. Weight x speed = kinetic energy = amount of energy to be absorbed by the vehicle.
Another misunderstanding seems to be based on how to judge safety -- it is not the amount of damage inflicted on the other vehicle; but rather the maximum forces exerted on the occupants. So, a vehicle that "shows" more damage is more likely to have protected the occupants better. Older cars are much less safe because they transmit more energy through to the occupants; instead of absorbing it.
For at least a couple of years now, the safest cars have been small to mid-sized sedans, like the Audi A4 and the Honda Accord, etc. They are well designed and have big enough crumple zones to protect the occupants, and they are not too heavy as to hurt their braking and accident avoidance handling.
Also, cars with better aerodynamics (i.e. lower and smaller) will have better handling, by definition. And smaller lighter vehicles will have better braking, too, all else being equal.
A neglected concept in vehicle safety (that I learned about from the folks at Edison2) is deflection; which is the opposite of engagement. Most vehicles today "engage" with whatever they hit in an accident, and the major problem with this is it shortens the time it takes to absorb the kinetic energy; making the peak forces on the people much greater. If a vehicle deflects away from the point of impact, then there is a much longer time to absorb the kinetic energy, and this tends to make the peak forces on the people much lower.
So, all in all, I would much rather be driving a lighter and well engineered car -- both for safety and for fuel efficiency.
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