I skimmed some parts I was already familiar with so maybe I missed a mention, but the issue with transitioning from straight to circular arc like this is you get an (theoretically) instantaneous change in lateral forces on the vehicle at the transition point.

Obviously it’s much less of a problem in a game, but it can look strange if you’ve implemented animations that make vehicles lean when going around curves or are limiting vehicle speeds based on those computed lateral forces.

In a game at least, there’s lots of simple ways to work around the issue (just use some kind of fake, arbitrary smoothing on changes in lateral forces).

In a real road, it would likely not feel good and probably would cause issues.