Abstract: A three dimensional road-vehicle modeling system includes a personal computer to store data on three dimensional road and virtual vehicle model, a real time simulator to run a simulation based on the data and model, and an actual test parts. A three dimensional course line of a vehicle is set on the three dimensional road. The simulator converts the three dimensional course line on the three dimensional road into a two dimensional course line on a two dimensional plane determined based on inclination of the three dimensional road and then converts the two dimensional course line into a straight course line corresponding to a three dimensional road model on the two dimensional plane based on hypothetical external force acting on the vehicle. These three dimensional road and virtual vehicle models are used to evaluate compatibility between the actual parts and the test vehicle.