I don't know if this is one bug or two.
Steps to reproduce (A)
1. Build a slope using the elevated ways system (e.g. "Sloped concrete head).
2. Try to build a road using click-and-drag up the slope (in the direction of the red arrows in the screenshot).
(https://cdn.discordapp.com/attachments/737992455361658891/1145122377244610631/image.png)
Expected results (A)
The road is built.
Actual results (A)
The road cannot be built.
Steps to reproduce (B)
1. Build a slope using the elevated ways system (e.g. "Sloped concrete head).
2. Turn on one-way display mode (using the colon : key in pak.128-Britain-Ex).
3. Select a one-way road tool using Ctrl+click.
4. Try to build a road using Ctrl-click-and-drag up the slope.
Expected results (A)
The one-way road is built and the arrows show this.
Actual results (B)
The road can be built, but the arrows initially show that traffic will be set in the opposite direction to that intended.