| | ABB Ltd. (ABB USA) http://www.abb.com |
| | Acela http://www.acela.com |
| | ADTC Est parisien http://www.multimania.com/adtcep |
| | ADtranz http://www.adtranz.com |
| | Advanced Railway Research Centre, Sheffield http://www.shef.ac.uk/uni/academic/A-C/arrc/ |
| | AEEFSJ http://www.ferrovia.com.br |
| | Afcalp http://www.afcalp.cl |
| | Agencia Nacional de Transporte P√∫blico de Brasil (ANTP) http://www.antp.org.br |
| | Agencia Nacional de Transporte Terrestre de Brasil (ANTT) http://www.antt.gov.br |
| | Agentes de Transportes Internacionales http://www.eaff.com.ar |
| | Alaska Railroad http://www.akrr.com |
| | Albanian Railways (unofficial) (HSH) http://www.angelfire.com/ak/hekurudha/index.html |
| | Alstom http://www.alstom.com |
| | América Latina Logística (ALL) http://www.all-logistica.com.ar |
| | Amateur (SCHWEIZERISCHER EISENBAHN) http://www.seak.ch |
| | American Public Transit Association (APTA) http://www.apta.com |
| | American Short Line and Regional Railroad Association (ASLRRA) http://www.aslrra.org |
| | Amtech http://www.amtech.com |
| | Amtrak http://www.amtrak.com |
| | Ankara Metro and Rail Transport http://www.ego.gov.tr/index-eng.html |
| | Asociación Amigos del Tranvía de Córdoba http://www.tranviasdecordoba.org.ar |
| | Asociación Latinoamericana de Ferrocarriles (ALAF) http://www.alaf.int.ar |
| | Associaçâo Nacional dos Transportadores Ferroviários de Brasil (ANTF) http://www.antf.org.br |
| | Association For European Transport (AET) http://www.aetransport.demon.co.uk |
| | Association of American Railroads (AAR) http://www.aar.org |
| | Association pour l´Histoire des Chemins de fer en France http://www.trains-fr.org/ahicf |
| | Associazione Italiana Studenti Ingegneria Ferroviaria (AISIF) http://www.aisif.it |
| | Atlas Model Railroad Company http://www.atlasrr.com |
| | Attiko Metro http://www.ametro.gr |
| | Australasian Railway Association (ARA) http://www.ara.net.au/ |
| | Austrian EU Council Presidencys´ Transport Information Service http://transport.bmv.gv.at |
| | Autoridad Marítima http://www.autoridadmaritima.gob.pa |
