Main Legal requirements

Directive 2004/52/EC of the European Parliament and of the Council of 29 April 2004 on the interoperability of electronic road toll systems in the Community:

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2004:200:0050:0057:EN:PDF

Directive (EU) 2019/520 of the European Parliament and of the Council of 19 March 2019 on the interoperability of electronic road toll systems and facilitating cross-border exchange of information on the failure to pay road fees in the Union

https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32019L0520&from=EN 

Commission Decision 2009/750/EC of 6 October 2009 on the definition of the European Electronic Toll Service and its technical elements:

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2009:268:0011:0029:EN:PDF

Other Legal requirements

Directive 2007/2/EC of the European Parliament and of the Council of 14 March 2007 establishing an Infrastructure for Spatial Information in the European Community (Inspire):

http://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=OJ:L:2007:108:FULL&from=EN

http://inspire.jrc.ec.europa.eu/

ITS action plan: Communication from the Commission — Action plan for the deployment of intelligent transport systems in Europe (COM(2008) 886 final):

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:52008DC0886:EN:NOT

Directive 2010/40/EU of the European Parliament and of the Council of 7 July 2010 on the framework for the deployment of Intelligent Transport Systems in the field of road transport and for interfaces with other modes of transport:

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:207:0001:0013:EN:PDF

Guide for the application of the directive on the interoperability of Electronic road Toll Systems (2011):

http://ec.europa.eu/transport/media/publications/doc/2011-eets-european-electronic-toll-service_en.pdf

COMMUNICATION FROM THE COMMISSION EUROPEAN COMMISSION, Brussels, 30.8.2012 COM(2012) 474 final - Implementation of the European Electronic Toll Service:

http://www.parliament.bg/pub/ECD/122425COM_2012_474_EN_ACTE_f.pdf

EETS REGISTRATION

As reference is the EC web address with the list of links per MS:

https://ec.europa.eu/transport/sites/transport/files/national_eets_domains_registers.pdf 

EETS relevant studies:

State of the Art of Electronic Road Tolling  (MOVE/D3/2014-259):

http://ec.europa.eu/transport/modes/road/road_charging/doc/study-electronic-road-tolling.pdf

Technology options for the European Electronic Toll Services:

http://www.europarl.europa.eu/RegData/etudes/STUD/2014/529058/IPOL_STUD%282014%29529058_EN.pdf