From: ahk@chinet.com   
      
   John Levine  wrote:   
      
   >>>That's how the Oyster system in London works.  When I was there last   
   >>>year, I used my US issued Amex card to tap in and out, and it billed   
   >>>me once a day for whatever I used.   
      
   >>The important feature of the Phoenix system is that it billed passengers   
   >>the lowest combination of fares, so that that the passenger didn't have   
   >>to decide to purchase a pass. That's not what you're describing.   
      
   >Oyster does indeed do day capping.  It'll never charge you more than   
   >what you'd have paid for a day travelcard.  It does have its   
   >limitations.  When I was in London last time, I realized as I bought a   
   >train ticket on the day I left that I'm old enough for senior fares.   
   >If I'd used my regular Oyster card, I could have asked a staff member   
   >at a tube station to do something at a turnstile that permanently   
   >flags the card so I get the senior fares but they can't do that for   
   >credit cards.   
      
   >Re the card reading terminals, since magstripes are pieces of magtape,   
   >the readers are subject to physical wear as the cards are swiped or   
   >dipped or whatever.  Sure, we have decades of experience keeping them   
   >going, but compare the card reader on a MTA bus with a slot and a   
   >motor and the one on a Muni bus, with no moving parts at all.   
      
   Nevertheless, the excuse in Chicago for buying Ventra (it's actually   
   leased) was that the contactless system we already had for 20 years   
   had to be replaced as it was proprietary and they weren't going to   
   make cards for it any longer.   
      
   There was no standard contactless card in those days, unless we had   
   bought the technology Hong Kong was using, which probably would have   
   been a good idea.   
      
   Every piece of technology has costs.   
      
   >>As far as complex transactions, given that the stripes get written to,   
   >>your position is unreasonable that any complex fare transaction couldn't   
   >>be encoded.   
      
   >Maybe, but I don't think I've ever seen a magstripe system that   
   >handled anything more complex than passes for a single system.   
      
   You're right. It would have been difficult having separate "banks"   
   encoded on a magnetic stripe, but it wouldn't have been necessary to do.   
      
   >>It's not actually necessary to write anything to fare media. These can   
   >>all be handled with back office transactions, with the card itself   
   >>used for nothing more than account ID.   
      
   >As I understand it, that doesn't work for performance reasons.  A   
   >turnstile can consult a server in the same station, but not the master   
   >one somewhere else.  TfL says an Oyster transaction has to take no   
   >more than 350ms, and they grudingly accepted 500ms for bank cards with   
   >a promise from the banks that the next generation will be faster.   
      
   We're talking about transit fares. All that has to be done in real   
   time is validate the fare media. The rest of it doesn't have to happen   
   immediately.   
      
   >>I don't understand why smart phones went with a different chip standard,   
   >>considering they wanted to get into the payment business. I thought EMV   
   >>was the older standard.   
      
   >EMV was designed in the early 1990s, and needs to work on cards with   
   >no internal power.  NFC is a decade newer and is a lot more flexible.   
   >It can't be that hard to do both -- just about every contactless   
   >point of sale terminal I try works with my NFC Android phone.   
      
   Ok, thanks.   
      
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