This paper deals with the development and validation of a methodology for the condition-based monitoring of railway pantographs and overhead equipment. The method is based on the use of simple vibration measurements, from which an estimate of the pantograph-catenary contact force is extracted using an Extended Kalman Filter estimator. The contact force estimate obtained is then processed to recognise the signature of typical catenary / pantograph defects: to this end, different approaches are applied, including spectral analysis and evaluation of statistical momenta. To demonstrate the feasibility of the proposed condition based monitoring methodology, an example of application of the contact force estimation procedure is included in the pa...