David Levinson:

Today we have cars. In 30 years we will have cars. But in the meantime, some cars will will driven by humans and others not, and there will be terms to distinguish them.
 Today, most people use the terms Autonomous, Automated, Self-Driving, and Driverless as interchangeable. Even wikipedia does not differentiate. Yet some people in the field make a point of the differences (e.g. Alain Kornhauser). If I understand these differences correctly, a self-driving car is not as advanced as driverless, in that driverless doesn’t have the back-up of a person taking control, and self-driving might. Driverless taxis are not merely self-driving, they pick up passengers and may be personless. In SAE terms, driverless is Level 5, while self-driving is Level 4 or below.