I think one reason roof pillars on cars are thicker these days is because the cars themselves are getting so darned heavy. Also, a sharply sloping roof pillar gives less support than one that's more vertical, and with the rakish windshields on modern cars, I think they have to beef up the B-pillar (central pillar) to compensate for strength lost on the A-pillars (windshield pillars)
As for cars that can withstand a 20 mph hit? They used to make them. The only problem is that the car survived, but they had to hose the occupants off of the dashboard!  I do know from experience though, that a '57 DeSoto can rear-end a '55 DeSoto hard enough to throw it about 20-30 feet, without either car suffering any damage! 
|