Travelers who are worried about their privacy are advised to "always try and use a prepaid chip card paid for with cash," said King. Using electronic transit cards in that way makes it possible to travel anonymously. Concerned E.U. travelers can also file a subject access request that requires European data processors to disclose what personal data they store, King added.
Privacy International plans to disclose more responses from transit authorities and companies on its website in the future. The organization has polled organizations in English, Spanish, Portuguese and French speaking countries, which will be given another month or so to respond, King said.
Loek is Amsterdam Correspondent and covers online privacy, intellectual property, open-source and online payment issues for the IDG News Service. Follow him on Twitter at @loekessers or email tips and comments to firstname.lastname@example.org