The design of vehicles, particularly hybrid and other advanced technology vehicles, is typically complex and benefits from systems engineering processes. Vehicle modeling and simulation have become increasingly important system design tools to improve the accuracy, repeatability, and flexibility of the design process. In developing vehicle computational models and simulation, there is an inevitable compromise between the level of detail and the development/computational cost. The tradeoff is specific to the requirements of each vehicle design effort. The assumptions and detail limitations used for vehicle simulations lead to a varying degree of result uncertainty for each design effort. This paper provides a literature review to investigate the state of the art vehicle simulation methods, and quantifies the uncertainty associated with components that are commonly allocated uncertainty. By understanding the inaccuracies and inconsistencies within these studies, improved simulation methods can be proposed. The consequences or accuracy of common assumptions are determined which will aid future simulation efforts as well as provide metrics for evaluating the appropriateness of past efforts. The results of this paper will aid future simulation design efforts and can begin to define standards by which simulation design studies are conducted.