Although roomy, quick and clean, the most interesting thing about Singapore’s underground system is not traveling on it, but planning your trip and purchasing your ticket (at least from an interaction design perspective). Both these steps are in fact integrated into one machine and are part of the same process:
The main interface of ticket machines consists of a screen embedded into a backlit map of the entire underground system. This map, however, not only visually aids the customer’s choice of destination, but is actually touch-sensitive. So after choosing, say, the single-ticket option from the screen on the left, customers select their destination by pressing the respective station.
If one assumes that the average traveler’s picture of the underground system is that of its standard map, then this process appears to be much more intuitive and ultimately superior to selecting a destination from a multi-page alphabetical list (as is the case in London or Berlin). This combination of selection and purchasing, however, also has its disadvantages as undecided customers may block the machines for those who know where they are heading.

Single-trip tickets are dispensed in the form of reusable plastic cards (contactless smart cards using RFID technology), for which a S$1 refundable deposit is payable (about 50 Euro cent). This approach not only saves ink and trees, but effectively eliminates any wastage resulting from used tickets, as the cards are fed back into the machine to reclaim the deposit.

It is somewhat peculiar, by the way, that I did not find any ticket machines at Changi Airport station to get my dollar back before flying home…