Ever wonder what happens when a brawny 6,000-lb. sport-utility vehicle collides with a typical 3,000-lb. sedan? Apparently, an insurance-company actuary hears it. Some big insurers are about to make it more costly to cover big vehicles than small ones. That's a break with the past. The reason? With record numbers of large vehicles like the Ford Expedition and the Chevy Suburban on the road, insurance companies are finding that drivers of the behemoths cause a disproportionate amount of harm to other cars and drivers, resulting in bigger liability payouts.
To offset the higher expenditures, insurers are boosting the premiums for liability...