If you’re using the splines to move AI bots, then it would be better to spawn units with sufficient intervals as to avoid collision between units along the same lane. Since you’re using tanks, they won’t have to stop and fire like the ranged AI bots that come with the toolkit. You could just rotate the turret and fire while moving. So that would negate any need to check for collision.
As for collision between units traveling along different lanes as shown in the screenshot, just increase the value of Lane Gap Distance variable in the Enemy Spawn Point actors. This will increase the gap between different lanes.