Limit RichAi pathfinding to a portion


Imagine I have a road which has two lanes!But I want the agents to find the path on 1/2 of the road so each agent can go on a line which is from (1/2 to 1) or (0 to 1/2).How can I control such behavior.

The other thing I wanted to ask is each time I play the game the whole navmesh gets regenerated and I don’t want it since I have done it out of play mode can’t I just use that?It takes too much time and the players get annoyed.