Hi i can do that using Ai over the street building the street as NavMesh , the cars NavMesh Agents,
so this will controll the Ai pathing on cars avoiding colitions , finding paths and choosing destination , and the street can be positioned in diferent Script Layers, so you can control where they can go , the speed at that area ,the direction of the street , with some triggers you can control stop lights , so cars stop when red light on crossroad, well yeah its all a very easy task a lot of minitask done on code, but all easy just depends on how much rules for traffic you want and stuff like that but yeah and all with Unity built in Navigation (NavMesh)