In message , at
05:50:38 on Thu, 7 Nov 2013, Neil Williams
remarked:
1. No unresolved journeys. The way I would work this is the same way as many other systems do it, such as Singapore - touching in charges the
maximum Oyster single fare to the card that could apply from that station (subject to cap if appropriate for London), and touching out refunds
back the difference back to the journey you actually made. If you don't touch out, you don't get it back, tough. That is powerful motivation,
and far, far less complicated.

The last one I had to sort out was my wife who arrived at Waterloo (on a
paper ticket) who was clutching her Oyster to make an onward trip on the
tube, and got psycho-babbled into "always touching" when she exited the
platform to the concourse.

TfL assumes this means "I've blagged a trip to here from somewhere
without a touch-in barrier" whereas to the traveller it means "I've
arrived in Oyster country, so start logging my trips from here onwards".
--
Roland Perry