This paper first outlines the effects of electronic technology on the automotive design process. In particular it concentrates on the design challenges caused by including signal data buses in the automotive system. A data bus simulation system, developed to overcome these designs challenges, is then described. This system is at present capable of simulating the S AE J1850 and Controller Area Network (CAN) protocols. The simulator is very flexible, and the final part of this paper describes examples of ways the simulator will be enhanced to allow more aspects of the automotive system to be simulated. These enhancements include: Other data bus protocols Combining the data bus simulator with other simulators. This will allow complete sub-systems to be assessed, by modelling both the mechanical and the data bus components together.