Robocars - Autonomous Drive, Self-driving, Driver-less cars

Just as car sharing lanes (2+) on the freeways and highways was quick to be established I see no reason why legislators won't in the name of environmental efficiency and public safety declare lanes for self-driving vehicles. As demand for these lanes increases it would be expected that the remaining lane capacity would be quickly eroded.

Most certainly. Not only that, but as enclosed motorised carriages will acquire even more of the nimbus of the 'universal transportation tool', other modes will increasingly be sidelined. (The myth of the universal tool is one of the main problems with car use.)

Also, there would be a renewed impetus for more highway capacity again. Greenwash around electric cars, the promise of largely crash-free environments (which I think is questionable at best) and the fact that people would probably be able to use the time spent travelling for other activities would soon cause people to forget about the real problems with driving, that they will spend even more time being inactive, and the social separation and isolation they're most likely going to increase, not to mention the dire consequences for land use patterns.