On Tue, 16 Sep 2008, Tim Roll-Pickering wrote:

Tom Anderson wrote:

It doesn't address the problem with recharging your oyster at night,
though. I would have thought that could be done fairly simply by having
some oyster machines - which could be of the card-only type - on the
outside of tube stations, and so accessible outside opening hours.

Great for the tube areas but what about those parts of London where the
tube is not within walking distance? Virtually all the shops that charge
Oysters that I know of close at least two hours before the tube does.

True.

The situation i was primarily thinking of is trying to get home after a
night out, where generally, i'm in the middle of town where there are lots
of tube stations. I would imagine this pattern accounts for the majority
of post-closing-time bus use, although of course not all.

I'm stumped as to how you could deal with the problem in the situation you
describe, though. Night buses don't take cash, so no solution involving a
chit is going to work. Putting chip-and-pin on buses seems like a
non-starter. I think that means you have to put fixed machines around the
place, taking either notes or cards, and dispensing either a fistful of
tickets (or a ticket and a chit) or oyster charge. Basically, the same as
the machines i want to put outside tube stations. You couldn't put those
at every bus stop, or even as many bus stops as have ticket-for-coin
machines, as they'd be too expensive (i assume). You could probably put
them at railway stations and key bus nodes (places like Clapton Pond,
say). Would that do?

One day, we might see oyster chargers as part of every cash machine. That
might largely solve the problem.

How about a mobile phone scheme? You text a special number, it charges you
two quid or whatever (as mobile phones sometimes do, i don't know how) and
sends you a code. The driver taps the code into a special gizmo on the
bus, checks to see if it flashes a green light saying the code valid, and
then prints you a ticket. The special gizmo could work in one of two ways.
Either it's in touch with a central server, in which case it just calls in
and checks your code, with the server then crossing the code of its list
of valid codes, or else it's standalone, in which case it can verify the
code using some cryptography. The problem is then preventing replay
attacks, where someone uses the same code more than once. You could
perhaps do this with a combination of time and space - codes could be
valid for 15 minutes after issuing, with the time being embedded in the
code, and only valid in the area from where the message was sent. You
could detect unused codes at end-of-day data reconciliation, and refund
the buyer, so people whose codes expired before they could use them
wouldn't be punished. To speed things up, the code could be in the form of
an image, ie a 2D barcode [1], which could then be read by a cheap little
webcam sat next to the driver.

tom

[1] http://en.wikipedia.org/wiki/Barcode#2D_barcodes

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