On Fri, 30 Dec 2005 00:17:44 GMT, Alix wrote:

If I go from a zone 4 station to another zone 4 station then I guess
Oyster would charge me for one zone.

But what if the route I took went via Zone 3 and I never left any
station in between? Would Oyster charge me for 1 zone or 2 zones?

All Oyster would know is that I started in zone 4 and left in zone 4.

Not so.

Or is Oyster a lot smarter than that?

Yes! It knows the exact stations you started and finished at.

FOR EXAMPLE:
(1) Get on the tube at South Woodford (zone 4, Central line).
(2) Must travel via Stratford (zone 3).
(3) Get off at Ilford (zone 4, railway station served by One Rail).

Charged for one zone or two zones?

As has been noted, pre-pay is not valid on 'one' to Ilford, but the
example can be fixed by using Barking instead. In that case, the
system knows that a journey from South Woodford to Barking must pass
through zones 3 and 4, and would charge you accordingly (in the same
way as if you went to the ticket machine at South Woodford and bought
a ticket to Barking, it would sell you a Z34 single rather than a Z4
one).

Actually, this still isn't a very good example as the Z34 fare happens
to be the same as the Z4 one, but anyway.

You may then ask, does it know whether you decide to go via Mile End
(Z2), in order to make the journey with just one change of train? The
answer is that it doesn't, and would still only charge you the Z34
fare. AFAICS there's no way you could be liable for any sort of
penalty fare, either.