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Waterslide Transit Systems

So ...

Barclaycard have introduced a slide-and-go payment system that allows a punter to leave the office via an alternative exit, purchase a banana in the supermarket and then head off, via the library, into the underground (or subway, as the cars all appear to be driving on the right), where a single beep sees him slip-sliding all the way home, to ask for a towel in what seems to be an up-north accent. 

I have performed a Griffo straw-poll and discovered that virtually everyone thinks that the advert is great, thinks that the waterslide is great, and thinks that the song is great, but no-one really has a clue about the message.  Most spotted the BarclayCard connection, and most recognised that by implication, it must relate to some sort of payment thingy, but no one actually spotted the payments being made - they are now all sitting in front of their tellys, waiting for 90 seconds of enlightenment, and the beeps.  

Good advert though!

It got me thinking, and now I guess I need some help from someone very clever, as I just don't get it.  I know that I can buy a banana, because I know how much a banana costs, assuming that bananas are sold by the banana and not by the pound, but even if they are sold by the pound, I can weigh and pay, and that would simply mean slowing down a bit to check the weight.  This is still not an issue, as I, and the POS systems, will know the total value of the transaction before the card is presented to the reader.  But how does that work on the underground?  The card is presented to the reader before the reader knows how much to charge, and the reader cannot know how much to charge unless I tell it where I am going, and there isn't much chance of that since I am wizzing through, in me trunks, waving the card as I pass.  Something clever is surely going on here.  The in-gate doesn't know where I am going, and the exit-gate doesn't care; even so, the in-gate must still charge me the right fare. 

How does the subway system know by how much to debit my account?


Comments: (5)

A Finextra member
A Finextra member 04 December, 2008, 13:51Be the first to give this comment the thumbs up 0 likes

Oh but the exit gate does care!... The entry gate will read the card and the exit gate will read where you left the system and charge you accordingly.

A Finextra member
A Finextra member 04 December, 2008, 15:22Be the first to give this comment the thumbs up 0 likes

So ...

What you are saying is that there is a contactless transaction on the way in and another contactless transaction on the way out.  That'll be two contactless transactions, both of which must have a monetary value of more than 0p.  Hmmm!  One low value ride split between two lower value contactless transactions.  I can see the business case faltering a bit here. 

Two questions for you?  First; on the way in, if you are not charging the full fare, how do you know the punter has enough money to pay on the way out?  Second; on the way out, how does the gate know where the punter got on?

And even if the exit gate does know where the punter got on, and can charge appropriately, what happens if the punter has no funds?


A Finextra member
A Finextra member 05 December, 2008, 05:33Be the first to give this comment the thumbs up 0 likes

I suppose you could stop them, not let them out of the gate, call them on their mobile and make them top up their account over the phone. If you have their number and there are probably a few other ifs in there somewhere, like if they have the money in their account.

Of course you could ditch the card and just use the phone without all the swipes and save all that infrastructure and confusion.

I'm sure the travelers would appreciate the lower fares or better service that could be provided with the money saved, unless of course they also owned shares in BarclayCard or swipe reader manufacturers.

I see plenty of room for improvement.

A Finextra member
A Finextra member 08 December, 2008, 16:48Be the first to give this comment the thumbs up 0 likes

Assuming you are referring to real-life, the way this is normally done is quite simple. The system debits the maximum cash-fare upon entry (on the tube, this is £4 I think), and refund the difference upon exit. There is, of course, the risk that the customer's balance is insufficient to cover the maximum cash-fare, even if they only want to use the system for a short journey. This is a risk that Transport for London, for example, is willing to take, and many a traveller have had to top up their Oyster cards when faced with this situation.

How the waterslide exit-gate is implemented is anyone's guess...

A Finextra member
A Finextra member 09 December, 2008, 11:08Be the first to give this comment the thumbs up 0 likes

Certainly that is what happens with the Oyster Card - debit on the in-gate and credit the difference on the out-gate - but then the balance is essentially held on the card, so credits (or refunds) are instant.  Now, let's look at a standard MasterCard / Visa transaction - the debit is made at the point of entry, for £4 if you like, and then at the point of exit a refund of £2.50 is generated.  However, the refund in this case is not in real time, and is submitted to the card issuer via the settlement process, which means that it could take up to 3-4 days to appear on the account.  That means that for me to complete 4 trips a day for 3 days, I would need an overall availabler balance of £48, to enable me to enjoy £18 worth of waterslide.

This is one of those questions where the devil is certainly in the detail.  The answer is obvious until you lift up the hood and have a look!

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