The biggest practical strides are those of safety. The car is surrounded by fields of invisible radar and festooned with cameras. It knows when other cars are crossing in front of you at an intersection, entering a blind spot or even likely to rear-end you.
In the last scenario, before a rear impact it will tighten your seat belts and automatically lock the brakes, so you’re less likely to plow into the car in front of you.
By contrast, the semi-self-driving features are destined to be used by drivers who text or e-mail in traffic. (Everyone agrees that is a no-no, yet I see people doing it all the time.)
The S550’s latest cruise control follows the flow of highway traffic, slowing or speeding up in relation to the car
in front of you. Your feet stay off brake and gas. The steering assist helps keep centered in the lane, tugging gently when your hand is on the wheel. It also keeps you from veering into oncoming traffic.