Creating complex 3d model

Hi

I am wondering wich method to choose when creating a complex 3d model of a testrack. It is almost 400m long and have a shpe of small "b". It has several downhill with various slopes to test vehicles.

My question is this.

Should i create the 3d geometry inside a 3d design file, where I create manualli the breaklines that bear up of the testtrack geometry...

Or should i use 2d design file with the 3d as a reference and use the "Horizontal Geometry" to create the geometry in 2d and 3d?

I am using Powercivil SS4 vers. 08.11.09.789

Regards

Sigfús