To digress from the OP's topic...
joker97: Just a word about safety. In a crash the heavier thing always wins.No, it doesn't. It equals two vehicles with identical mass colliding while both travelling at 60kph. This is due to Newton's third law. The Mythbusters show this in one of their episode and iihs outline this in their description of the test.
The NCAP stars are strictly tested on low speed and simple collision.
Say one sided front collision at 60kph.
That equates to a head on crash with both cars going at 30kph (30 + 30=60).
joker 97: If you crash at 70kph (say travelling at 100 and emergency brake for 0.5 secs) with the other car at 70 that is a 140k collision.If the other car is twice your weight you will get nearly the entire force. Airbags or not won't do squat.It's not a '140k' collision. The two vehicles will impart the same force on each other (3rd law). What you may have been getting at is that the deceleration will be twice as high in the smaller car (inversely opposite to the difference in mass).
So the physics do dictate that you are better off being in the larger vehicle. Of course if everyone takes this approach, then we all end up driving very large vehicles and we're essentially no better off, except our fuel consumption is through the roof. This is one factor (among many) as to why the US has such large cars. However, how vehicles are able to deal with deceleration has a major impact on how well it protects the occupants of the vehicle.
The other interesting thing is that a Holden Commodore, a 'big car', is only 600kg (or 60%) heavier than a Jazz (~1000kg). So it still has to deal with a considerable amount of deceleration. Far from doing squat, airbags, crumple zones, passenger safety cells as a collective go a huge way towards mitigating the effect of crashes in smaller vehicles.