
I have a feeling one-way bits on every other grid would be best, as then it would be impossible for any vehicle to drive on the wrong side of the road, while keeping the ability to build intersections: Also one-way bits at both ends of any bridge or tunnel so they can't be used to go the wrong way either.
Ownership of the roads isn't that big of a problem for me, as I start my games from 1885. So the WmDOT builds a few roads, goes bankrupt, and then starts up again

My thoughts on the pathfinder (without almost any knowledge how difficult they would be to implement

- Only allow a limited amount of turns for motorways, maybe max 2-4. This makes them both faster to travel on & look more... dominating I guess.
- Don't make them go directly from city to city, but rather start & end just outside of a city, with a road into the city: These could then be expanded further to longer and longer distances.