On Sat, 3 May 2008 14:15:40 -0700 (PDT), MIG wrote:

A passenger touches in in Zones 1 & 2 with Zones 1 & 2 travelcard, then
touches at Beckton. Did they change onto the DLR from LU, or did they leave
at an ungated LU station then travel to Beckton by some other means?

If less than 2 hours pass between touch-in and touching at Beckton,
the system assumes the former. If more than 2 hours, the system
assumes the latter.

(This is irrespective of whether the passenger touched at Bank.)

A similar point arose a while ago. This is, in certain circumstances,
effectively a ban on starting a second journey within a certain time
period.

If the passenger wanted to start a second journey, couldn't they just
touch at Beckton twice? (OK, so in this example they'd get charged
extra.) Or would the validator reject a second touch in too short a
time?

The other story was someone getting charged for two unresolved
journeys due to starting a new journey at Bow being treated as a
continuation of the same journey which then went over two hours. (Why
the system can't recalculate it as two journeys, particularly in a
situation where it's clear where the person has been, I don't
understand.)

Because, if PAYG uses a state model (a system of logic flow for
deciding what happens when each touch occurs), and it works the way I
think it does[1], this is actually very difficult to achieve. It would
involve adding lots of data and logic to the system, which would make
it more expensive to design and implement, for little perceived
benefit.


[1] Mizter T, if you're reading this and still keen on experimenting,
here's one that would help here. When you do an out-of-station
interchange, what happens if you miss out one of the touches at the
interchange? For example, if you travel from Ravenscourt Park to
Goldhawk Road, normally you touch 4 times:
1. Touch in at Ravenscourt Park
2. Touch out at Hammersmith (D&P)
3. Touch in at Hammersmith (H&C)
4. Touch out at Goldhawk Road

There are 2 experiments he (a) What happens if you miss out #2
(i.e. do 1, 3, 4)? (b) What happens if you miss out #3 (i.e. do 1, 2,
4)?

I *suspect* that in both cases, you'd actually get charged the same
amount, and have the same journey history, as if you'd done all of 1-4
(though I'm less sure that this would be the case in (b)).

You'd need some method (tailgating, paper Travelcard, other Oyster
card, etc) to get through gates without touching when required.