2004/49/EC is the Railway Safety Directive; it has since been amended by Directive 2008/110/EC. It harmonised safety principles, including procedures for granting safety approval to railway operators and infrastructure owners.
Directive 2004/50/EC
Directive 2004/50/EC harmonised interoperability requirements, particularly for high-speed rail. It amended Directives 96/48 and 2001/16; it has since been updated by 2008/57/EC.
Directive 2004/51/EC
Directive 2004/51/EC allowed open access for freight services, nationally and internationally, starting in January 2007
Regulation (EC) 881/2004
Regulation 881/2004 created the European Railway Agency, to coordinate safety and interoperability efforts.