Curve with different Radii

Hi guys,

Im stuck with a angle calculation for a curve with different radii.
Depending on which direction the Radius is going (so up or down, left or right) the angle calculation needs to be minus or plus.
The angle is calculated through vectors, which are defined through lines from my tunnel blocks.
But with the calculation its always a plus value. Not depending on the type of radius.
I could do that manually and define it myself, but It would be perfect if that would work automatically.
For better understanding of the problem I have attached a few screenshots.
If something is not clear please let me know.
Any idea?

try to take the vector from Line.Direction, get the Y value, and take the sign from it + or -, then add it to the vectorAngle

I tried something like that already, but it works only for a few Blocks. In this case the only 9 last Blocks would have a minus value.
Its hard to define that situation.