Hi ISH
One way roads will change to Two way if it is in anyway connected to another Two way road/Street (even if the connection is by Invisible Road).
One Way roads are notorious for spawning car/cars heading the wrong direction, a little wrinkle I use is to "bleed" that traffic off if by adding a spline a short way from the start off the road and leading a length off invisible road from it into the bush or behind a building ending it out of sight.
NormP.
BTW, If you are using 'TWO' one-way roads side by side (as a Hwy) I have also connected them together (just like a railway crossover) at a convenient place with
Invisible road so that the wrong lane traffic will cross from each Road, note the crossing must be in the same direction as the wrong traffic.