In CT-MQC and CT-TSH both the electronic and the nuclear equations of the exact factorization are approximated, as described above. Therefore, a question that is indeed interesting to address is: How well can one hope to reproduce nuclear dynamics using trajectories? To answer this question, we introduce the concept of quantum trajectories, as trajectories that are propagated under the effect of the exact TDVP and TDPES . For a model system, the TDVP and the TDPES can be computed numerically exactly from the output of vibronic wavepacket dynamics. Furthermore, if a gauge is chosen such that the TDVP is the nuclear momentum field , then the simple equation