Chris6791 said...
Dont be fooled by the crash test between the Mercedes sedan and the Smart car. Apparent crash damage and rigidity of the passenger cell is not a true indicator of survivability. One of the biggest factors to prevent serious internal injury is the rate of deceleration in a crash, the more car you have to crumple around you the longer it takes for the crash forces to be absorbed - which it what you want. Arguable in most instances you want to get out of a car crash and see a crumpled wreck that is a write-off, it means the engineers have done a top notch job.
Watch the top crash test a few times, the Mercedes at the point of impact has more mass, energy and momentum and decelerates through the point of impact and rolls on another metre or two, now watch the Smart car, not only does it decelerate to a stop at the point of impact in the same instant it changes direction and goes back where it came from, that incredible deceleration and direction change will kill ya. Thats where all the internal injuries come from.
Smart cars are great for congested inner city travel where average speeds are way down, if I lived out in the 'burbs whee speed limits are higher and interaction with trucks at higher speeds is more likely I wouldn't consider it.
The Smart car weighs 750 kg, the S class 2,000 kg, F-ma. The force on the Smart car is equal and opposite to the force on the Mercedes, so yes the deceleration in the Smart is 2.7 times that of the Merc.. For this reason the Ancap ratings are only comparable if you assume the car has hit another of the same weight and crumple rates. I recall Mercedes was considering making the crumple zones on its larger models overly soft, so that the accelerations imparted to the occupants of another standard weight car would be the safety criterion in a standard crash. I didn't hear that Mercedes carried this idea through, the large cars would be too fragile when accidently backed into a lamp post. All things being equal you're better off in a heavy car, the battleship mentality, part of the reason there's so many 2 tonne SUVs charging down to the shops for a litre of milk.
(Although once the car hits something with many times the weight and zero crumple, like a truck, the ANCAP tests scores once again become comparable. The truck won't lose much speed whatever the weight of the car, so it's analogous to hitting the immovable concrete block of the NCAP test. A 30kph head on with a truck going 30kph is the same as an NCAP test at 60kph which is the same as a 60/60 kph head on with an identical car.
