Design-for-accessibility is becoming a global requirement. While much has been done to achieve high levels of accessibility in rail transportation, not much has been done to improve the safety of these vulnerable users in the event of heavy braking and, in a worse case, crash. The kinematics that ensues after the crash governs the secondary collision characteristics, injury mechanism and ultimately injury severity. Fundamental analytical understanding of the factors that influence crash occupant motion is required to ensure kinematics that has reasonable accuracy. This is key in providing well informed and accurate input data and establishing realistic boundary condition; particularly when commercial software is applied like a ‘black box’ without delving into the fundamental dynamics behaviour. The general wheelchair occupant kinematic model presented in this paper is initially based on the ideal condition for safety as applied in road vehicles. The data and information obtained from the model equations are, however, invaluable to providing input data and boundary conditions that result in more realistic commercial software FE model results.