Development of a system to obtain vertical track geometry measuring axle-box accelerations from in- service trains

Nowadays, metropolitan railway systems are in great demand, so they offer highfrequency services for the most part of the day. Therefore there are only a few hours during night available to carry out maintenance tasks. This research develops a system that records the vertical accelerations undergone by the bogies of in-service railway vehicles. As accelerations are measured during regular services of trains, no additional vehicles or personnel are needed and maintenance planning is optimized. Accelerations are processed to obtain the vertical track alignment in order to determine whether the track needs to be repaired. The developed system has been validated by comparing its results to the actual state of the track provided by a track monitoring trolley. Comparison is made both by graphical and statistical methods. Real data come from measurements taken on Line 1 of the Alicante tram network (Spain). This paper presents the data collecting procedure, the mathematical processing of the accelerations and the analysis of the track condition.