Supposedly, the Euler spiral is difficult to build. Therefore a compromise has been made with a multi-radius transition. The transition curve passes through a couple of decreasing rediuses before it reaches the corner with constant radius.

Hmm.. maybe there is a standard, such as banking angle / arc segment, tfor any oval race track.

@TigerGuy, what factors determine the rate of banking progression (from 10° to 30°). Is it a linear or non-linear progression and the rate of progression.