But all things being equal Rater irrational requirement, given that we're talking about engineering. It short circuits the entire conversation. In any case, I

But all things being equal Rater irrational requirement, given that we're talking about engineering. It short circuits the entire conversation. In any case, I find it odd that you find my reference of the Smart "humorous". While the IIHS held their results as demonstrating bigger versus smaller, in actual reality it primarily demonstrated more expensive versus less expensive -- there is no great confusion that less expensive cars often sacrificed safety, and this was true at all vehicle sizes (e.g. some early budget Kia minivans and SUVs were deathtraps). It seems to have mostly passed now that even economical cars like the Cruze are posting stellar results. But let's assume that a greater weight, by itself, equals better safety. So would that Volvo do better than the Tesla if they filled the trunk full of concrete blocks? Note that I didn't say that weight doesn't correlate with safety, but that it doesn't correlate nearly as strongly as you seem to imply -- e.g. saying that a large sedan is 1000lbs heavier than another large sedan in no way, I would guess, leads to a conclusion that it will also do better in safety tests.