On 27 May 2006 12:06:42 -0700, "MIG"
wrote:

I can't help answer that, but I've got another question which maybe
someone can answer at the same time.

If you bleep in (somewhere ungated like the DLR or a bendy bus) and it
tells you that you haven't got enough money, does it assume that you
are starting a journey or not? Given the possibility of negative
credit, maybe it would.

As you say you are entering the DLR or the bus then the system will
assume an entry is being made - subject to what is on the card for your
last journey.

The bus validation will be simple enough - it will just look to see if
you have a positive value of cash or are within zone / date (depending
on ticket type). If these factors are fine then a transaction will be
completed that either deducts cash for pre-pay or simply records the
basic journey details for the Travelcard.

On DLR the validation checks will be similar. If you had an entry record
for your last trip and it was within journey time and date parameters it
is likely the validator would assume you were exiting rather than
entering. This would either deduct or add back the appropriate cash for
Pre-Pay or just add an exit transaction for a Travelcard.

If your last trip was outside of time parameters and all other factors
were OK the validator would assume a start of a trip. If the cash
balance was sufficient for the entry deduction then a valid entry
transaction would be written to the card. This would then be used by the
exiting validation equipment wherever you got off to deduct the due
value from Pre-Pay (either for a whole journey or a part journey if
travelling as an extension to a Travelcard ticket on the card).

If you were not in zone or had insufficient funds then your card should
be rejected and no transaction would be written to the card.

The above is my understanding of how the logic should work.

So if, having got the message, you then got a paper ticket (because it
was the DLR, say, and you had no time to find a shop) and went where
you were going, would you be left with an unresolved journey and
negative credit, or assumed to have travelled without a ticket or what?

If you buy the paper ticket you are not travelling without a ticket. If
you are unable to top up your card for a Pre-Pay trip or are out of zone
then your card would not have an entry transaction and you would be
travelling without valid authority on the network. I do not see how you
could have an unresolved journey from the beginning of your trip - it
would only be unresolved if you attempt to exit DLR or LUL at the end of
a trip where you decided to enter the system out of zone or without
sufficient funds for the Pre-Pay deduction on entry.

I may have missed the point you are trying to get clarified so if there
is a real life example - as I'm sure there is - then that may well help.
--
Paul C


Admits to working for London Underground!