I think autonomous car operation will only be found in one place, the place that GM envisioned as far back as 1939: on limited access freeways. In short, when you drive on the freeway, you set it for the posted speed limit and a bunch of vehicles travel at the same speed on the freeway (with full compensation for amount of traffic and weather conditions), and there are special sequences to engage and disengage autonomous operation when you enter or exit the freeway.
Actually, autonomous car operation is more likely to be found in congested cities where safety is less of a concern because travel speeds are low. I think Pittsburgh just rolled out a pilot program with fully autonomous taxi cabs in the center of the city.