This paper is about position estimation and fault detection under jamming fault for rail transportation system. The motivation is to improve the accuracy of the position estimator in real-world conditions, considering modeling errors, perturbations and expected faults. The approach is based on an unknown input observer used to estimate perturbations and detect jamming faults for a class of polytypic linear parameter-varying (LPV) system. Moreover, the mixed H∞/H_ approach is applied to help in the robustness of the fault detection via a residual. Offline experiments results are provided for illustration.