That link has a short tutorial on it at the bottom.
Note, for TS2010 the cars must be kind 'scenerytrackside'. As such, you will need to convert the traffic. I'm currently (in my own time) working on a tutorial and converter set for this purpose, using the mesh-library functions.
Thanks zec
Do I have to get permission to use the cars in them??
If it's that easy, I am now a region builder! I'll make a sports cars one, vintage cars one and anything else I can think of
Jamie