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.
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.
Fun to wait at the entrance with a motorcycle. As soon as it’s open you have 5 miles where it’s physically impossible for another car to merge on.