To use public transport in some Australian capital cities, you have to use a card (for use with proximity readers). When you buy the card you can buy it anonymously or you can buy it and register it to your name. Either way, the card has a unique number. (Registering it to your name could be good if the card is lost or stolen.)
If you register the card to your name then, like a mobile phone in a sense, you are carrying a tracking device. As you move around the public transport network, each time you enter or leave a bus, train, tram or ferry, a location record can be created against your name.
If you keep the card anonymous, then those location records can still be created but they can only be associated with you if your use of the card can be associated with you e.g. through the use of manual or automatic facial recognition via the extensive network of surveillance cameras or e.g. if you choose to transfer money into the card’s account to top up the balance (and you do of course have to have a non-zero balance in order to travel) and you transfer money in a way that can be associated with you (and I suppose likewise when you buy the card you make a choice about payment method).
(So realistically an anonymous travel card may not be very anonymous.)
I hope this gives an understanding of some of the privacy challenges of public transport in my country. Hence
