TAMPA, Fla.—As auto makers gear up to offer technology that automates the most grinding parts of a daily drive, getting customers on board could be the easy part. It is the regulators and insurance companies that may need the hard sell.

Between now and 2016, an increasing number of car makers will offer "traffic jam assist" systems that take over braking, steering and acceleration for vehicles inching along in low-speed traffic. It is a far cry from Google Inc.'s vision for a car that can drive itself in all conditions,...