After our articles about elevating roads, upgrading roads and building curve roads there is article about one-way roads and how to change direction in them. It will be quick to pass on the essentials quickly. So let’s start with building one way roads.
How to change one-way directions?
As I promised, I’ll start with how to change the direction of the one-way. Same as I’ve wrote in article about upgrading roads you must select “upgrade mode” of building roads…

… and there is one rule. If you select other type of road then which you have build. And you click with “left click” then you upgrade road.
But if you click with right click on your mouse then you change direction of one-way road. On image bellow you could see that I changed middle segment of road and now you could see new “T-icons”…

… this “T-icons” signalize that you don’t have connected this one-way road properly. You could have problems with traffic because from this segment cars can’t go over. So you must change all segment of your one-way road to fit it.

Where to build one-way roads?
One-way roads in Cities Skylines has big arrow over them which shows you direction of traffic and they are builded like other roads. Direction is “selected by” starting point from which you start. Arrows will always point to your destination.

I’m using one-way roads to optimize traffic in resident zones when you know that there won’t be a lot of traffic. On one-way roads for mine perspective is better parking options and they looks better with car.

Same as in resident zones one-way roads could be great for industrial zone to increase flow of trucks. One highway exit I usually use for arrival to zones and I use one-way four or six lanes for high “bandwidth”. And in the exit point I don’t have exit I have just connection to the highway.
This isn’t best when you have strong internal traffic because cars must go on highway to other city districts. But it depends on how you make levels.