Electric traction is key to decarbonising railways, but there are challenges and uncertainties in the cost of electrification. Overhead line electrification (OLE) structures and their foundations have contributed to cost and programme overruns in the UK, in part owing to uncertainties in the structural loads transmitted to the foundations. Improved understanding of these structural loads, particularly the dynamic components from wind and train aerodynamic effects, is essential to reducing the cost and uncertainty associated with the design and construction of OLE structures and their foundations. This paper describes the initial development of a suite of instrumentation to record synchronised wind velocities, structural strains and accelerations on in-service OLE structures. The monitoring system aims to establish both the effects of wind loading for comparison with design code coefficients, and the structural dynamic response to trains passing at speed. Strain measurements at the base of the foundation and at the OLE cantilever connection will identify the structural loads transmitted into the foundation pile cap. Accelerometers will be used to assess the structural displacements caused by wind excitation of the structure along with exploring potential coupling between adjacent OLE structures. Key findings from a preliminary instrumentation deployment in a non-operational setting are presented and the implications for in-service field deployment at a variety of sites across the UK rail network are discussed, along with the implications of the improved understanding for geotechnical design.