"Gradually, almost imperceptibly, Tom Harrison began to lose flexibility in his neck and trunk. He was in his early 80s. There are worse things at that age, right?

Then a test offered by Greenspring, a community for older people in Springfield, where Harrison lives, revealed that the stiffness limited his view while driving. Harrison couldn't turn well enough in his seat to identify an object on a computer screen behind him, which meant he would have trouble doing the same thing behind the wheel."