I'm not sure the impact of the self driving car will be as profound as you think. First, people already consume media in the car -- unless you drive in silence, you're sitting around listening to the radio, podcasts, streaming music, something. Second, while we may be able to increase our consumption concurrency for that period of time, I'm not entirely sure it's new consumption -- it's just displacing radio. It could also drive consumption down if people choose to work in the car and not consume any media at all -- they can't do that today because they're busy driving.

The big problem with using media measurement to gauge media consumption is that we can really only measures access, not consumption. The advertising world is built around impressions for that reason; there's an implicit assumption that some percentage of "impressions" will go unnoticed. Measuring that and trying to get your ads in a format where they will be consumed more often when they are shown is pretty much the focus of the entire advertising industry. For a very concrete version of this, think of how DVR users skipping commercials has led to an increase in product placement within shows.