High quality terrain and roads

how would I go about creating terrain and roads at a quality as good as Dirt Rally?

Which tools would you recommend?

Note i only care about visual quality and accurate road physics. I don’t need pathfinding or AI and it’ll be static except a few objects.

 

The physics will be determined by the vehicle, not the road. There is a good free path-painting tool here:

https://github.com/Roland09/PathPaintTool

For actual roads, EasyRoads 3D free is basic:

https://assetstore.unity.com/packages/3d/characters/easyroads3d-free-v3-987

Otherwise, if you have money then EasyRoads 3D Pro on the asset store is great:

https://assetstore.unity.com/packages/tools/terrain/easyroads3d-pro-v3-469