csts
as defined in Directive (EU) 2016/798 of the European Parliament and of the Council of 11 May…, Article 3, point (5) (Definitions)
the minimum safety levels that are to be reached by the system as a whole, and where feasible, by different parts of the Union rail system (such as the conventional rail system, the high-speed rail system, long railway tunnels or lines solely used for freight transport);