Real world roads and tracks follow the principle that the curvature changes linearly with the curve length. This has the advantage that at constant driving spee

Real world roads and tracks follow the principle that the curvature changes linearly with the curve length. This has the advantage that at constant driving speed the steering wheel has to be turned with constant speed as well. So, the curve should really be a clothoid, sometimes called Euler spiral, but a cubic Bézier can be a good enough approximation.