Most autonomous driving architectures separate planning and control phases in different layers, even though both problems are intrinsically related. Due to limitations on the available computational power, their levels of abstraction and modeling differ; in particular, vehicle dynamics are often highly simplified at the planning phase, which may lead to inconsistency between the two layers. In this paper, we study the kinematic bicycle model, which is often used for trajectory planning, and compare its results to a 9 degrees of freedom model. Modeling errors and limitations of the kinematic bicycle model are highlighted. Lastly, this paper proposes a simple and efficient consistency criterion in order to validate the use of this model for planning purposes.