You could open up lanes a quarter mile at a time even depending on traffic demands.
Eg. Between exit 1 and exit 2, 8 northbound lanes are open. Between 2 and 3 we have 6 northbound lanes.
It's would be pretty disconcerting to travel in your self driving car and head full speed into oncoming traffic only to shift lanes a few moments before collision though.
They had this in Montreal back in the day (i.e. the 1960s, when the risk of a head on crash was one you just accepted by driving).
There would be a bunch of lanes undivided from each other and over the lanes would be lights telling you which lanes were open for your direction of travel.
Movable barriers work too but are far more expensive.
Eg. Between exit 1 and exit 2, 8 northbound lanes are open. Between 2 and 3 we have 6 northbound lanes.
It's would be pretty disconcerting to travel in your self driving car and head full speed into oncoming traffic only to shift lanes a few moments before collision though.