When combined with so-called "active cruise control," systems that use cameras, radar and other sensors to detect vehicles on the road ahead and maintain a safe following distance, a driver could, theoretically, drive on a highway without actively steering or touching the gas or brake pedals.
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Mercedes-Benz (DDAIF) and Infiniti (NSANY), among others, offer systems like this in their cars today. One key aspect of their systems, though, is that the driver must keep hands on the steering wheel at all times. If I were to take my hands away for even a few seconds, the car would remind me to grab the wheel again. Otherwise, the system would quit and I'd have to take full control.
These systems have become very sophisticated and work well on highways, even in stop-and-go traffic. But they aren't designed to handle city streets or complex intersections.
Many automakers and technology companies are trying to make autonomous cars work well in cities. BMW recently announced that it will have city-capable autonomous cars by 2021.
The highway where Brown died was particularly problematic, because it allows left turns across traffic without traffic lights. That combines the hazards of both cities and highways. Situations like this are a challenge for human drivers as well as the engineers that design autonomous cars.