This video just has me thinking:
http://www.ebaumsworld.com/video/watch/80712005/
The Smart was crash tested at 40 mph against the Mercedes at 40 mph. Due to the gross difference in weight, it would appear that the impact equivalence to each is closer to 60 vs. 20 mph. Clearly the Smart driver is at the losing end of this one. Now imagine the same test against an SUV or full size pickup.