Robin May wrote in message ...

The way Oyster works is that if you touch in at a station (any station,
LU, DLR or NR) within the zones of your travelcard you won't be charged
if you don't touch out.

Indeed. But this doesn't always seem to work smoothly. For instance: I
have a Z1-3 monthly on my Oyster. Every day I touch in at the gates at
Farringdon and take Thameslink to Herne Hill (no barriers, no Oyster
readers). Lots of other people do the same thing. I was quite
surprised (last time I looked at the usage history on one of the big
machines) to find out that it had been recording
"Farringdon-Uncompleted Journey" for each of these. This doesn't
happen when, for example, I touch in at London Bridge and get off at
West Norwood (also no barriers). All these uncompleted journeys don't
seem to be having an adverse effect. Is this happening because of
Farringdon's strange status as a Tube station which just happens to be
served by grown-up trains?