With the advent of European Train Control System Level 3 (ETCS L3), Siemens Mobility has condensed the diverse set of related specifications, European working group analyses and solution proposals into a holistic onboard perspective on ETCS L3 operations. The technical implications for the train integrity device have been derived by employing a strict user perspective. Furthermore, this article hints at an ambiguity in the corresponding European railway Agency (ERA) solution proposal (CR940) which is rooted in the existing lack of a harmonised risk analysis for determining “safe train length”.