In message , at 05:18:08 on
Sun, 25 Mar 2012, Charles Ellson remarked:
If I touch in twice at a National Rails station with my Oyster, will it
be registered as a start of journey?

If you mean twice on entry then IIRC there has to be a minimum time
between touches for the second one to count as it is an expected event
for this to happen if e.g. a gate jams or someone thinks there has
been no response to the touch.
Unfortunately it isn't among the combination of touches dealt with in
this FOI request :-
http://www.whatdotheyknow.com/reques..._card_more_tha

A quick Google suggests that, at least with buses, a second touch
gives a signal to the driver (who will hopefully have seen it has been
in the same person's hand on both occasions) but does not incur an
extra charge. That seems to match my personal experience when the
validator on a bus was either "dumb" or was overpowered by background
noise.

What happens at stations seems to depend on whether or not they are
gated so I'll let someone else answer that.

If a station is gated, then the second touch won't work, because it's a
measure to prevent "pass-back fraud", in other words handing your Oyster
over the barriers to a friend so they can "share" it.

If the station isn't gated, then pass-back fraud isn't an issue, but
Oyster cards can't be shared (even legitimately) by two concurrent
travellers, and more to the point the validators are two-way, so the
rule of "Touch in at a validator then touch out at a [the same]
validator" would apply. (see question 4 of the above FOI enquiry).

viz: "Within two minutes of touching in .... it is not possible to
touch out on a validator. The validator will perform a
Continuation Entry, leaving the card with an open journey and the
Entry Charge (maximum Oyster fare)."
--
Roland Perry