A simple two-mass-spring model was developed to describe the dynamics of car-to-car collisions. The characteristics of the spring in this model can be chosen as a piecewise linear function. The model was applied to determine the dynamics of a range of crashes and to compare the dynamics of a car-to-car crash with the dynamics of crash tests. Furthermore, the model was applied to evaluate the crush length available in current cars. It showed that a large share of the current car fleet already offers enough crush length to ensure a compatible behaviour. Despite of the simplicity of the model, it can be used in an effective way to give a quick insight in the basics of real life crashes compared with laboratory crash tests. A future step is the augmentation of the model to a multi-mass-spring model by means of the software program MADYMO.