Low voltage DC powered railway systems have significantlosses in the power network. This paper presents interimresults from a project which aims to measure simultaneouslythe power output from substations and power input tovehicles. Data have been recorded in initial instrumentationtest runs on both a vehicle and two substations. Theinstrumentation system performed adequately and the qualityand accuracy of the data are appropriate to meet the overallobjectives of the study. It is possible to see details in thecurrent waveforms, such as notching currents, from theinstrumentation located on board the train and at thesubstations.