I think the multiple critical paths makes the most sense. I'm guessing each road is a project unto itself and within the road, the work to complete that road is related. The only relationship between the road is resources. You've resolved the overallocations by leveling. Project does not take resources into account when displaying the critical path - only the task schedules.

Thanks. I think your idea to consider each road as seperate project is good.

/Møller