This article is based on the RTR Special issue on wayside train monitoring systems published in March 2011. Of course, the present article can only give a short summary of all the material included. The growing importance of wayside train monitoring systems in European railways is driven by three main factors. First is operational safety to compensate for the loss of human inspection of passing trains at stations due to remote controlled interlockings and centralization of operations control. The second element can be found in the availability of the European freight corridors. Preventive recognition of upcoming fault states allows immediate interaction and thereby increasing quality of transport due to reduced disturbances of traffic flow. Last but not least, the third factor is the usage of measured data for maintenance purposes. This requires a well established information storage and distribution platform to provide reliable data to potential user groups.