Irreversibility and forceback in public interfaces

We are starting to see walk-up kiosks and self-service machines everywhere in the public space. Indeed, it seems to be increasingly prevalent that service providers offer technological aid to customers so that they can perform more of the work entailed for themselves. Buying train tickets, checking in luggage at the airport or paying duty for excess merchandise upon returning home from abroad are examples of such walk-up-and-use services. It is surprising how such "simple" systems are not perceived as user-friendly. We believe that designing information technology for the public space poses distinct conceptual challenges. Yet, this has not been systematically explored within our field. This paper is based on an ethnographic study of the purchase and validation of ticketless travel for an airport train. It argues that public IT needs an extended framework of usability principles, which goes beyond well-known interaction design guidelines.