On Aug 10, 7:55*pm, asdf wrote:
On Sun, 10 Aug 2008 10:56:02 -0700 (PDT), MIG wrote:
I think it's the OP's wording that's confusing me. *It read as if the
£2 was coming up when he went through the barrier at Stratford, rather
than when he got off at Canary Wharf.

However, having gone through that barrier, he ought to be deemed to
have gone via Stratford anyway, one would have thought.

Arg. No. Can we please put this misconception to bed once and for all?

The Oyster system does NOT have an internal representation of the Tube
map, on which it runs some sort of AI software, to dynamically work
out what route you've taken, taking into account any touches you may
have made along the way, and from that work out what zones you've
passed through.

Instead, it simply takes the origin and destination, and looks up in a
static table what zones that journey is considered to have passed
through.

In other words, its data is of the form "Hampstead Heath to Canary
Wharf (Jubilee) is a Z12 journey", "Hampstead Heath to North Greenwich
is a Z23 journey", etc.

Intermediate touches do NOT make a difference to this.

(The exception is that if you travel from A to C with an intermediate
touch at B, and the A-B fare is higher than the A-C fare, you get
charged the A-B fare for the A-C journey.)

But what's the difference between calculating fares between
intermediate touches and calculating fares between end points? I
can't see that it would require different software from that which
handles OOS interchanges and the rest. Oh well. It was an aside
anyway.

I still haven't had a chance to do DLR to Hackney with a zone 1 and 2
travelcard loaded on Oyster and touching in on the DLR in zone 2/3,
and seeing if it's charged zone 3 to my PAYG balance. This is mainly
due to the demise of the DLR most weekends and a pretence at a life.