Keep in mind that a lot of traffic collisions with pedestrians or other vehicles happen when lights change and cars need to (suddenly) slow down.
Person A might slam on their brakes at the first sight of a red light. Person B make floor it to make the light. Put person A and B in the same lane and they might hit each other. Or in different lanes person B might blast through the red light right as a pedestrian started crossing.
Predictability is the most important thing. Unfortunately I’m not sure how much I trust an AI to be predictable.
Also when I’m walking and when I’m driving I want as little intersections as possible. There are other ways to slow down traffic besides awful intersections.