Recently Madrona Ventures, in partnership with Craig Mundie (former Microsoft CTO) released a white paper proposing an autonomous vehicle corridor between Seattle and Vancouver on I-5 and BC Highway 99. While there are some useful ideas in it, the basic concept contains some misconceptions about both traffic management, infrastructure planning, and robocars.
Carpool lanes are hard
The proposal starts with a call for allowing robocars in the carpool lanes, and then moving to having a robocar only lane. Eventually it moves to more lanes being robocar only, and finally the whole highway. Generally I have (mostly) avoided too much talk of the all-robocar road because there are so many barriers to this that it remains very far in the future. This proposal wants to make it happen sooner, which is not necessarily bad, but it sure is difficult.
Carpool lanes are poorly understood, even by some transportation planners. For optimum traffic flow, you want to keep every lane at near capacity, but not over it. If you have a carpool lane at half-capacity, you have a serious waste of resources, because the vast majority (around 90%) of the carpools are "natural carpools" that would exist regardless of the lane perk. They are things like couples or parents with children. A half-empty carpool lane makes traffic worse for everybody but the carpoolers, for whom the trip does improve.
That's why carpool lanes will often let in electric cars, and why "high occupancy toll" lanes let in solo drivers willing to pay a price. In particular with the HOT lane, you can set the price so you get just enough cars in the carpool lane to make it efficient, but no more.
(It is not, of course, this simple, as sometimes carpool lanes jam up because people are scared of driving next to slow moving regular lanes, and merging is problematic. Putting a barrier in helps sometimes but can also hurt. An all-robocar lane would avoid these problems, and that is a big plus.)
Letting robocars into the carpool lane can be a good idea, if you have room. If you have to push electric cars out, that may not be the best public goal, but it is a decision a highway authority could make. (If the robocars are electric, which many will be, it's OK.)
The transition, however, from "robocars allowed" to "robocars only" for the lane is very difficult. Because you do indeed have a decent number of carpools (even if only 10% are induced) you have to kick them out at some point to grow robocar capacity. You can't have a switch day without causing more traffic congestion for some time after it. If you are willing to build a whole new lane (as is normal for carpool creation) you can do it, but only by wasting a lot of the new lane at first.
Many are attracted to the idea that robocars can follow more closely behind another vehicle if they have faster reaction times. They also have the dream that the cars will be talking to one another, so they can form platoons that follow even more closely.) The inter car communication (V2V) creates too much computer security risk to be likely, though some still dream of a magic solution which will make it safe to have 1500kg robots exchanging complex messages with every car they randomly encounter on the road. Slightly closer following is still possible without it.