High automation means the system takes over longitudinal and lateral control; the driver is no longer required to permanently monitor the system. In case of a take-over request, the driver must take-over control with a certain time buffer.
High automation . . . is nonetheless challenging because it describes an automated driving system that, once engaged, can always revert to a "minimal risk condition" should a human driver not resume actively driving. Reverting to this minimal risk condition may be easier in some contexts (e.g., low-speed parking facilities) than in others (e.g. urban expressways) For this reason, a highly automated driving system is capable of operating in some, but not necessarily all, contexts or 'driving modes.'
High automation . . . is where the 'everything somewhere' strategy begins. The custom vehicles that currently operate without any real-time input from human drivers are limited to highly specific contexts, including particular routes and low speeds.