I thought this wasย interesting from the September issue of Car and Driver “Upfront” section:

Automakers define โ€œautonomyโ€ according to a scale established by SAE International (formerly the Society of Automotive Engineers). The scale tops out with control-free pods at Level 5, but even adaptive cruise control counts as Level 1.

What most people think of as full autonomy begins with Level 4, in which a car can handle the complete driving task without needing to defer to a human driverโ€”in certain cases. Think of a car that can drive on the highway but may need a human to take over at the exit, or one that can navigateย ย metropolitan areas that have been 3-D mapped in excruciating detailโ€”and at enormous costโ€”by companies eager to cut their overhead by eliminating human drivers. Leading innovators at two of the industryโ€™s largest and most powerful suppliers tell us they expect Level 4 autonomous vehicles to hit our roads by 2020, but only for fleet use. For the foreseeable future, the requisite technology will remain prohibitively expensive for private owners. And if youโ€™re waiting on a Google pod of your own, donโ€™t hold your breath. In even the best technophilic outlook, cars like that donโ€™t start to become widely available and affordable until 2050 or so. But our own expectation trends closer to never. Is never good for you?

Read more here (subscription only).