Any existing Reeds-Shepp implementations?
Copy of my comment above (I suppose that the question can be accepted/closed):

I think that the question is not research level, however perhaps this can help you: 
http://msl.cs.uiuc.edu/~lavalle/cs326a/rs.c (README: http://msl.cs.uiuc.edu/~lavalle/cs326a/README_RS).

You can also take a look at Chapter 13 of the book "Planning algorithms".