Not exactly. Polar is r-theta. The system we used was an x-y system, but one where the coordinate system alignment changed for each track segment. So, think of a world where a straight line in y ["longitude"] was projected into a constant path relative to the centerline of the track's racing surface.
(While most NASCAR tracks are ovals and could be represented in polar coordinates fairly naturally, they do have some road courses and the physics and game engine originated in the IndyCar game, which has even more road courses.)
Wow, that's amazing, a lot of time spent on that game :) Thanks for a great game!
Your coordinate system make sense, and the 3D engine/physics was pretty good for something running on CPU only. (If I remember there was only one or two non-oval tracks)
(While most NASCAR tracks are ovals and could be represented in polar coordinates fairly naturally, they do have some road courses and the physics and game engine originated in the IndyCar game, which has even more road courses.)