You can travel around (scanning your contactless debit / credit card) without thinking about how much you’re paying, safe in the knowledge that the system caps your daily / weekly spend to predefined limits, essentially making it never more expensive than a daily / weekly travel card would be. The caps are automatically calculated for the zones you travel in.

It’s a very nice experience as a rider. Especially beneficial to visitors who can just scan through the gates as any Londoner would, no ticket purchase required.

As for the rationale to implement such a system — well, it’s ultimately a public service. All revenue generated is reinvested into the network, in London at least. The economic value of a fast, efficient, painless transit system that everyone uses, regardless of class or wealth, most surely outweighs any lost breakage revenue.

Because people from far away are less likely to imagine ever needing an Oyster again, yet might still need one right now (especially before contactless payment cards would work just as well for most short term visitors) there was a scheme where you could just "donate" your card to charity at places like airports, I don't know if it still exists.

Because Oyster is variable fare even in the simplest scenarios (a trip from Stockwell to Brixton for example, versus a train going from central London out to Amersham at the far end of the line are different prices, before any consideration about season tickets, time of day etc.) it is possible to have a card that's valid to enter the system (it has enough money that you could make some trip) but then make a trip it can't pay for. In this case the balance on the card falls below zero on exit, to use it again you'll need to first pay the excess and enough for a ride somewhere. So you'd expect to see some number of cards discarded in this state, since they are in some sense less than worthless. But the inconvenience of needing a new card seems to out-weigh that.

London gets this (mostly) right, because there "contactless card" includes Visa/MasterCard/Amex/Maestro credit and debit cards, and smartphones with equivalent contactless payment. The local transport card (Oyster) is only needed for other fares (e.g. child-rate tickets) or season tickets of a month or longer.

Travel from Heathrow, Gatwick, Stansted and Luton airports is included in this.

(The only thing they could improve is the signage at Heathrow. They promote the expensive Heathrow Express train, when many people would be better taking an Elizabeth Line train on the same rails — 15 minutes slower and ¼ the price.)

(One more thing, last month they seem to have introduced a £5-£7 cost to get an Oyster card, which seems needlessly extortionate for visitors that do need them. Years ago it was a small deposit, which you could get returned in cash at the machine.)

[1] https://tfl.gov.uk/fares/how-to-pay-and-where-to-buy-tickets...

On day one there was no noticeable symptom. But if your Oyster only had a season ticket for outer Zones and your route was via Zone 1 the system had surcharged you, and when you tried to travel the next day the Oyster has negative balance, you can't use it until you pay off the excess. This infuriated some travellers, when in reality they had actually been cheating (presumably in most cases without realising) previously.

Today Oyster can actually track if you insist on taking the long route, you tap pink validators at key interchanges you'd need to pass through to do your slower and less central route avoiding Zone 1, and the system will go OK, fair enough, you really did go the long way so keep your money. I expect very few people do this.

Let's say I get on and 'tap in' at London Euston then travel to oxenholme (no ticket barriers, but a 2-3 hour £60 trip) if I don't tap out what should I be charged? This would have to be the same amount as if I travelled one stop on the tube in London and forgot to tap out. What if I tapped in at London got off the train after one stop and tapped out without leaving the station then continued my journey?

What minimum amount should my oyster card (or debit card) have on it in order to take a tap in? It would have to be ~£2.55 as that's the minimum fare; yet once in I could take a £200 train journey.

A big part of why the London system works is that it's quite literally small beer. The journey price range is something like £2.55-£9; in that case you can afford to do all sorts of things like have someone tap in with £2.55 on thier card and tap out with a negative balance, and generally cope with a small number of edge cases and loopholes that are an inherent part of providing contactless travel.

Comparing the process in London to that of, say, Paris, it is night and day better with London’s system. Yes, trips might cost more than a flat rate, but you don’t need to have a special card - contactless payments are charged at the same rates as an Oyster card would get charged, including discounts if you take multiple trips in a day.

Compare to Paris where it’s a flat rate, but you can’t get a normal ticket because your anonymous card is somehow designed only for tourist pricing. Let’s not even bother with how long the lines can be to buy said card. I’ll take a system where you tap on and tap off any day of the week over a flat rate system that doesn’t support easy contactless payment at the same rates as everybody else.

I should clarify though - this only applies to any travel by train that you can do from stations that have contactless to stations that also have contactless. Anywhere else, you’re expected to tap off and pay a normal fare for the rest of your travel to an unsupported station by buying it from a website.

And while it is unusual to have such complexity, I should mention that rail travel between countries often has similar complexity - I bought a ticket once from Copenhagen to Malmo, Sweden, but got on a train operated by a different company and had to buy a second ticket - the trains left at the same time to and from the same stations but from two different operators. The confusing part is that the train ticket I needed to buy wasn’t available from a Denmark regional train travel ticket kiosk, it was timed ticket you had to buy in advance from a website as the train’s origins was in Sweden rather than Denmark. (And the Denmark station didn’t have Swedish kiosks.)

I guess what I’m saying is that trains can make airlines look efficient, at least when it comes to buying and handling tickets. ;-)

Edit: I should also mention if I got any of this wrong, I’m actually from North America and about all I can say in response is “at least you have (express, high speed) trains,” as I look at our preference for highways and buses and how most rail in North America is for cargo...

As a commuter there I'm sorry, but I'd rather have saved a few quid a month on my ticket than pay for some tourist who can't figure out a credit/debit card despite travelling to one of the world's most expensive cities.

150 years ago you could lose a paper ticket or leave it at home, or it could have been out-of-date when you thought it wasn't, and you'd also be walking.

As for recommendations for tourists, Oyster is great, but, there's really no need, a contactless bank card is capped at the same day and week rate as Oyster.

I've been commuting for the last year on my bank card, it's not the most financially efficient way, but it's not a lot more expensive (than a pre-paid pass).

Also bear in mind that a bank card will take ~2 seconds to scan at most stations' gates, versus milliseconds for an Oyster. It might seem trivial but at London rush hour it's an annoyance for you and everyone else.

One thing people also don't know is that at most stations, your card won't scan if you're standing between the gates, step back and scan or you'll just hold everyone up until you give up and walk away.

It's designed this way, I imagine, so that you don't scan while someone is still paying through the gate and have it close on you before you pass through.

Oyster's PAYG pricing only covers daily travel (either the whole day or the off peak). For a week or longer yes you should buy (on Oyster) a fixed duration travelcard in advance. But let's continue the thought experiment.

If you travel in zones 2-3 for work you would want a Travelcard for those journeys, indeed, and you'd likely buy that for an Oyster (I believe paper tickets for this still exist, but they might not) which is £27.70 per week, or maybe you do this constantly that's £1108 for the whole year.

However that work travelcard covers zone 1 anyway, so the tourist trips into zone 1 are free for you.

Suppose the tourist trips are instead outward, and you're entering zone 4. Now these trips aren't free, but the day travelcard that includes zone 4 is £13.90 and the Oyster cap to zone 4 is £10.60 so you won't save money by buying another travelcard for the tourist trips, using PAYG with the cap is significantly cheaper and easier.

One thing a careful Londoner might do if the tourist friend is visiting for a bit longer and they (for some reason) don't carry a very long period travelcard or it was due to expire anyway, is choose to "upgrade" to more zones for say one week and then buy their usual card again. Suppose your card runs out on Friday, your friend lands Saturday morning and you're taking a week off exploring Greater London with them. You could buy a zone 1-9 weekly card from Saturday to Friday, just under £100 for all trips almost anywhere in the network for that week.

However, the tourist gets almost as good a deal on their foreign credit card because it has a weekly cap, the TFL credit card system thinks only in Monday-Sunday weeks, so their maximum cost is £135.10 for the same trips (two days, plus one week) but if they sometimes don't hit the daily caps it'll be far lower, so even just two "quiet" days with fewer journeys or staying in central London would demolish the price difference.

This statement is sensationalist and not true, as the maximum load on a Oyster Card is £90.

This is wrong. You can pay with an Oyster for Thameslink services out of and through London for example and drink on those. It literally only applies to Tfl operated services.

So I assumed I'd need a "tourist" Oyster as I wasn't a resident. But when I looked in to it as a tourist you had to book well in advance so they can post a card to you - whilst if you ignore the "tourist" offering you can just pick up the card at your arrival station (Victoria for me, very easy, was from a machine IIRC). Also the charges seemed higher for tourists somehow and there seemed to be difficulties giving the card back and getting a refund - I could see no reason to have a tourist Oyster.

One of the kids travelled free, with me, as it happened which was great. The only problem is that the automated turnstiles wouldn't let us through separately without us paying twice (for which we'd need a different Oyster) and I got "munched" on a couple of occasions one of which gave me a very sore back, it was quite vicious.

Traveller beware!

We only have these cards due to historical quirk (quick contactless technology existed, but not in credit cards), and if we lose them, it’s another thing that we’re never getting back.

(I protested the removal of paper tickets from Sydney’s trains and busses, for what it’s worth…)