• Our booking engine at tickets.railforums.co.uk (powered by TrainSplit) helps support the running of the forum with every ticket purchase! Find out more and ask any questions/give us feedback in this thread!

How do TfL readers actually work?

Status
Not open for further replies.

Sultan

Member
Joined
6 Mar 2019
Messages
232
mods note - split from this thread.

How do these TFL readers actually work? They ask you to tap your Oyster of Credit/Debit Card on the reader but how does it know the card has been tapped in somewhere? Considering the reliability of internet connections, I can't see that the portable reader checks in with the central system looking for the card and when / where it was last used.

Does the card itself somehow register that it has tapped in? Probably not where, just a flag to say there is a pending transaction.
 
Last edited by a moderator:
Sponsor Post - registered members do not see these adverts; click here to register, or click here to log in
R

RailUK Forums

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
97,532
Location
"Marston Vale mafia"
How do these TFL readers actually work? They ask you to tap your Oyster of Credit/Debit Card on the reader but how does it know the card has been tapped in somewhere? Considering the reliability of internet connections, I can't see that the portable reader checks in with the central system looking for the card and when / where it was last used.

Does the card itself somehow register that it has tapped in? Probably not where, just a flag to say there is a pending transaction.

It's in essence a "special tap in" which results in a PF being charged to the card in the back-end if it hasn't been tapped in first, I think.

Buses are different because the inspectors' device downloads a list of tapped-in cards on that bus when they board, so a PF or MG11 can be done on the spot.
 
Last edited:

swt_passenger

Veteran Member
Joined
7 Apr 2010
Messages
31,262
How do these TFL readers actually work? They ask you to tap your Oyster of Credit/Debit Card on the reader but how does it know the card has been tapped in somewhere? Considering the reliability of internet connections, I can't see that the portable reader checks in with the central system looking for the card and when / where it was last used.

Does the card itself somehow register that it has tapped in? Probably not where, just a flag to say there is a pending transaction.
It’s quite different for traditional Oyster PAYG and contactless debit/credit cards. With Oyster your credit balance is stored on your card, you tap in and a certain maximum amount is deducted on entry, (the system has no way of knowing where you’re going at this stage), and when you exit the correct fare is determined and your card balance is re-adjusted. The main thing is your card has an up to date balance.

The way contactless “transit mode” works is that the whole days travel, ie each successive entry and exit, is stored up, and overnight a back office processing system calculates the various fares to charge you and presents one amount to the bank for payment, after daily or weekly capping has been applied. When the OP of this thread says he’d tapped in so he’d paid his fare, he’s not quite correct. He’s tapped in and his journey has commenced, but the destination is still unknown, and it won’t be paid for until later, ie overnight. Nothing ever gets written to the contactless card.

An onboard check is basically an extra event that gets fed back to the processing system and if it matches a previous touch in it effectively does nothing. If you’re not already in the system it commences a new journey. But AIUI, and as you suspect, the onboard checking staff won’t know this because they don’t have real-time information. (However they do know if checked on a bus.)

I understand that after a certain number of onboard checks occuring when not already touched in the card will be hot-listed and you won’t be able to use it. Others will know for sure.
 
Last edited:

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
97,532
Location
"Marston Vale mafia"
I rather suspect that it suits operators like Merseyrail for the matter to remain in the murk though.

Merseyrail, notably, were attempting to use it for a very specific reason - to get round the fact that prosecution under the Byelaws or other relevant parts of RoRA is statute-barred if a Penalty Fare was issued and correctly appealed according to process (whether that appeal was successful or not).
 

Sultan

Member
Joined
6 Mar 2019
Messages
232
It’s quite different for traditional Oyster PAYG and contactless debit/credit cards. With Oyster your credit balance is stored on your card, you tap in and a certain maximum amount is deducted on entry, (the system has no way of knowing where you’re going at this stage), and when you exit the correct fare is determined and your card balance is re-adjusted. The main thing is your card has an up to date balance.

The way contactless “transit mode” works is that the whole days travel, ie each successive entry and exits, is stored up, and overnight a back office processing system calculates the various fares to charge you and presents one amount to the bank for payment, after daily or weekly capping has been applied. When the OP of this thread says he’d tapped in so he’d paid his fare, he’s not quite correct. He’s tapped in and his journey has commenced, but the destination is still unknown, and it won’t be paid for until later, ie overnight. Nothing ever gets written to the contactless card.

An onboard check is basically an extra event that gets fed back to the processing system and if it matches a previous touch in it effectively does nothing. If you’re not already in the system it commences a new journey. But AIUI, and as you suspect, the onboard checking staff won’t know this because they don’t have real-time information. (However they do know if checked on a bus.)

I understand that after a certain number of onboard checks occuring when not already touched in the card will be hot-listed and you won’t be able to use it. Others will know for sure.
Thanks for this explanation. With regards contactless, (I think) you're saying that an on-board check for a rail (not bus) journey, because it doesn't have real-time information (is this confirmed?), the checking staff won't know if that card was used to tap in. Or have I got this wrong? What would happen in an instance where you tapped in with one card, but inadvertently tapped a different one on the checking machine? Maybe this is better for a new thread in 'London Underground' section rather than this one.
 

swt_passenger

Veteran Member
Joined
7 Apr 2010
Messages
31,262
What would happen in an instance where you tapped in with one card, but inadvertently tapped a different one on the checking machine? Maybe this is better for a new thread in 'London Underground' section rather than this one.
That gets complicated. I think the answer will depend on which card you eventually use to tap out. But it’s probably getting too far off topic now...
 

Bletchleyite

Veteran Member
Joined
20 Oct 2014
Messages
97,532
Location
"Marston Vale mafia"
Thanks for this explanation. With regards contactless, (I think) you're saying that an on-board check for a rail (not bus) journey, because it doesn't have real-time information (is this confirmed?), the checking staff won't know if that card was used to tap in. Or have I got this wrong?

In my understanding that's correct. The penalty, if necessary, is charged in the back-end. There doesn't really seem to be scope to carry out a prosecution unless the RPI had for instance observed someone jumping a barrier rather than touching in.

What would happen in an instance where you tapped in with one card, but inadvertently tapped a different one on the checking machine? Maybe this is better for a new thread in 'London Underground' section rather than this one.

A Penalty Fare is charged to the card, I believe.
 

Haywain

Veteran Member
Joined
3 Feb 2013
Messages
14,869
Thanks for this explanation. With regards contactless, (I think) you're saying that an on-board check for a rail (not bus) journey, because it doesn't have real-time information (is this confirmed?), the checking staff won't know if that card was used to tap in. Or have I got this wrong? What would happen in an instance where you tapped in with one card, but inadvertently tapped a different one on the checking machine? Maybe this is better for a new thread in 'London Underground' section rather than this one.
I suspect that @MikeWh might be able to clarify this, but it would be better in a thread of its own.
 

Sultan

Member
Joined
6 Mar 2019
Messages
232
In my understanding that's correct. The penalty, if necessary, is charged in the back-end. There doesn't really seem to be scope to carry out a prosecution unless the RPI had for instance observed someone jumping a barrier rather than touching in.



A Penalty Fare is charged to the card, I believe.
So back on topic (of sorts), when you tap on the checker, it is 'holding' a penalty fare against that card (how much?) that only gets charged should it not detect (overnight?) that the card was used to tap in and out for the journey. By refusing to do this, you are accepting to have your details taken and then prove by other means that you had a valid ticket.

I think I can see what the easiest option is here - and if you're concerned about tapping a contactless card, get an Oyster card, register it with an account and set up auto-top up (this is what I have).
 

XAM2175

Established Member
Joined
8 Jun 2016
Messages
3,469
Location
Glasgow
So back on topic (of sorts), when you tap on the checker, it is 'holding' a penalty fare against that card (how much?) that only gets charged should it not detect (overnight?) that the card was used to tap in and out for the journey. By refusing to do this, you are accepting to have your details taken and then prove by other means that you had a valid ticket.
There is no pre-authorisation of a penalty by the inspection device itself; it simply records that a particular contactless card was presented for inspection at a certain date and time. The scan records are then matched overnight to the records of ordinary touches at gatelines and validators. If a suitable record of entry cannot be found, a penalty is charged.

As others have noted, this is no longer relevant to the OP's situation and needs its own thread if it's to go further.
 

MikeWh

Established Member
Associate Staff
Senior Fares Advisor
Joined
15 Jun 2010
Messages
7,865
Location
Crayford
I suspect that @MikeWh might be able to clarify this, but it would be better in a thread of its own.
I think the detail is best clarified here because there are some key points missing.

If you touch your contactless card/device on a Revenue Inspection Device (RID) on a train then all that will happen is a note is made of the card number (encrypted) and the precise time of inspection. The inspector only knows if the card is (a) not working, or (b) has been blacklisted, and in both cases will then go onto issue a penalty fare or fill in a MG11. If the card is a working contactless card then that is the end of the interaction. This is one of my favourite aspects of CPAY revenue protection because it takes the discussion away from the human to human on the train situation.

At some point the inspectors reader will upload details of all checks made to the TfL back office. There it will sit alongside all the other touches in, out or on pink readers until the end of the day. The system works through all the touches in order to see what journeys were made. As long as the card was logged as touched in at the time of an inspection then all is well. If it is not touched in then the revenue inspection turns into a maximum journey charge. This is a special maximum journey charge which will not be overruled without concrete evidence of issues at the touch in point. My understanding is that if you touch out at the end of the journey then you won't be charged a further incomplete journey charge, but I'm not 100% on that. If you touch in, get checked, but don't touch out then it is treated as a normal incomplete journey.

Like all maxiumum/incomplete journey charges they are added to your daily charge but they won't count towards any capping. The request to claim money will be delayed by a day in case there was an issue which delayed touches reaching the back office that might resolve the issue. If nothing changes you'll be debited for your journeys including the maximum fare. You can recieve two inspection charges and pay only the maximum charge, but after the third event your card will be blacklisted.

One further key detail is that your journey history will show the revenue check regardless of whether it triggered a charge or not.
 

ianBR

Member
Joined
4 Jan 2015
Messages
98
The above suggests that you should only ever use a contactless card (rather than Oyster). If something goes wrong with a touch-in on a contactless card, all that will happen is that you'd be charged a PF at the end of the day.

With an oyster card you are then at the whim of the ticket inspector who could choose to report you for prosecution rather than issuing a PF. I can't see any benefits of using an Oyster given that.
 

MikeWh

Established Member
Associate Staff
Senior Fares Advisor
Joined
15 Jun 2010
Messages
7,865
Location
Crayford
If something goes wrong with a touch-in on a contactless card, all that will happen is that you'd be charged a PF at the end of the day.
It is NOT a Penalty fare. It is a maximum journey charge.
With an oyster card you are then at the whim of the ticket inspector who could choose to report you for prosecution rather than issuing a PF.
With normal tickets you are just as much at the whim. It depends what you say and/or how you say it.
I can't see any benefits of using an Oyster given that.
If you want to attach a railcard discount. If you want a period travelcard or a weekly not starting on a Monday.
 

lookapigeon

Member
Joined
18 Dec 2009
Messages
86
If you want to attach a railcard discount. If you want a period travelcard or a weekly not starting on a Monday.

I have never understood why such things can't be attached to the 'token' of the credit/debit card you are using, so that when you tap in it will know, I mean the system is smart enough to detect blacklisted/hot cards?

Also from casual observation on a bus or at the tube, I have noticed a lot of people who use the cards stored on their phone tend to get the double beep/issues with the gates or reader and thus hold up the line. Is it just that people do not get the phone ready to be tapped in/out beforehand?
 

MikeWh

Established Member
Associate Staff
Senior Fares Advisor
Joined
15 Jun 2010
Messages
7,865
Location
Crayford
I have never understood why such things can't be attached to the 'token' of the credit/debit card you are using, so that when you tap in it will know, I mean the system is smart enough to detect blacklisted/hot cards?
A blacklist/whitelist system is pretty much off the shelf. Adding a third list not so easy.
Also from casual observation on a bus or at the tube, I have noticed a lot of people who use the cards stored on their phone tend to get the double beep/issues with the gates or reader and thus hold up the line. Is it just that people do not get the phone ready to be tapped in/out beforehand?
Possibly, or they're just not proficient at using that function of the phone.
 

zwk500

Veteran Member
Joined
20 Jan 2020
Messages
13,223
Location
Bristol
A blacklist/whitelist system is pretty much off the shelf. Adding a third list not so easy.
Given that the transactions are all processed at the end of the day, would it not be possible to allow users to add the Railcard (or whatever it is) to their TfL account with which the card is linked, and apply the discount as appropriate when the final reckoning is done? If checked mid-journey the user has still tapped in, so there would be no problems with fare enforcement, and as the discount is added to an account the entitlement to the discount can be verified before it is applied.
 

XAM2175

Established Member
Joined
8 Jun 2016
Messages
3,469
Location
Glasgow
Given that the transactions are all processed at the end of the day, would it not be possible to allow users to add the Railcard (or whatever it is) to their TfL account with which the card is linked, and apply the discount as appropriate when the final reckoning is done? If checked mid-journey the user has still tapped in, so there would be no problems with fare enforcement, and as the discount is added to an account the entitlement to the discount can be verified before it is applied.
Because the Railcard association cannot be written directly to the card, and there's no guarantee that Authorised Officers would have live access to the TfL accounts database whilst on patrol, it wouldn't always be possible under such a system to check that the bearer of the discounted card also holds the matching Railcard at the time of travelling.

It would theoretically be possible to work around this limitation by having the revenue inspection devices carry the full list of Railcard-to-contactless-card associations, which would flag a card presented for inspection as only being valid with the associated Railcard, but this would be a major software change on top of the changes that would be required to set up the overall Railcard-on-contactless system, and it would need close scrutiny to identify any potential security or data protection risks.
 

zwk500

Veteran Member
Joined
20 Jan 2020
Messages
13,223
Location
Bristol
Because the Railcard association cannot be written directly to the card, and there's no guarantee that Authorised Officers would have live access to the TfL accounts database whilst on patrol, it wouldn't always be possible under such a system to check that the bearer of the discounted card also holds the matching Railcard at the time of travelling.

It would theoretically be possible to work around this limitation by having the revenue inspection devices carry the full list of Railcard-to-contactless-card associations, which would flag a card presented for inspection as only being valid with the associated Railcard, but this would be a major software change on top of the changes that would be required to set up the overall Railcard-on-contactless system, and it would need close scrutiny to identify any potential security or data protection risks.
Apologies if i wasnt clear. When travelling, the passenger would effectively be paying a full adult fare. The Railcard would not be linked to the card itself, and RPIs would not see a Railcard discount, but a full adult fare.
The Railcard would be linked to the TfL account, and the discount is only applied after a journey is complete, if it is eligible for the discount. If its possible for the capping to be processed after the fact, surely the railcards could be as well?
 

Adam Williams

Established Member
Joined
2 Jan 2018
Messages
1,704
Location
Warks
there's no guarantee that Authorised Officers would have live access to the TfL accounts database whilst on patrol, it wouldn't always be possible under such a system to check that the bearer of the discounted card also holds the matching Railcard at the time of travelling
Given how ubiquitous mobile coverage is nowadays, these arguments don't really convince me anymore. We have 4G on the Jubilee, WiFi at most other tube stations - you could implement it with a bloom filter that gets refreshed at every point where there is coverage available - even if every person in the UK owned a railcard it'd still fit into 100MB.

How do you think on-national-rail-train revenue inspectors retrieve scan history for a scanned e-Ticket/determine if it's cancelled?
 
Last edited:

najaB

Veteran Member
Joined
28 Aug 2011
Messages
30,691
Location
Scotland
Given how ubiquitous mobile coverage is nowadays, these arguments don't really convince me anymore
Ubiquitous, but not universal and uninterrupted. And you can pretty much guarantee that the time its needed the most will be the time that it's not available.
 

Adam Williams

Established Member
Joined
2 Jan 2018
Messages
1,704
Location
Warks
Ubiquitous, but not universal and uninterrupted. And you can pretty much guarantee that the time its needed the most will be the time that it's not available.
Simple fix: Require customers to wait 1 day before travelling for their Railcard discount to take effect.

You can refresh the bloom filter at least once a day, I refuse to believe a revenue inspector can be outside of mobile data coverage for an uninterrupted 24 hours.
 

trebor79

Established Member
Joined
8 Mar 2018
Messages
4,435
I understand that after a certain number of onboard checks occuring when not already touched in the card will be hot-listed and you won’t be able to use it. Others will know for sure.
So what happens the next time you don't tap in, and present that card for an onboard check?
 
Joined
7 Jan 2010
Messages
11
On the rail card point, I think TfL have committed to delivering something on it as part of their bid for the wider South East contactless contract
 

Mojo

Forum Staff
Staff Member
Administrator
Joined
7 Aug 2005
Messages
20,382
Location
0035
I have never understood why such things can't be attached to the 'token' of the credit/debit card you are using, so that when you tap in it will know, I mean the system is smart enough to detect blacklisted/hot cards?

A blacklist/whitelist system is pretty much off the shelf. Adding a third list not so easy.
As someone who was involved with the early stages of the implementation of the Revenue Inspection Devices, the reason given at the time that it would not be possible to keep the system live at all times. As designed originally the system synched with the live server over 3G and it was quite clear that it would not be possible to keep up with the frequency with which the data would have to refresh. Especially on the Underground which as we know the majority of the sub-surface stations and trains did not at the time, and even still does not, have mobile data access. Bear in mind that at the early stages it was not even clear whether National Rail services would even be accepting Contactless Payment Cards.
 

XAM2175

Established Member
Joined
8 Jun 2016
Messages
3,469
Location
Glasgow
Apologies if i wasnt clear. When travelling, the passenger would effectively be paying a full adult fare. The Railcard would not be linked to the card itself, and RPIs would not see a Railcard discount, but a full adult fare.
The Railcard would be linked to the TfL account, and the discount is only applied after a journey is complete, if it is eligible for the discount. If its possible for the capping to be processed after the fact, surely the railcards could be as well?
I'm afraid I still don't see how this addresses the concern about the bearer's entitlement to use the Railcard. Remember, the Railcard is only valid for use by the person to whom it has been issued, and this is established in the present system by the revenue inspector checking that both the ticket and Railcard are presented together. How is this check performed - or replaced - in your proposal?

Given how ubiquitous mobile coverage is nowadays, these arguments don't really convince me anymore. We have 4G on the Jubilee, WiFi at most other tube stations - you could implement it with a bloom filter that gets refreshed at every point where there is coverage available - even if every person in the UK owned a railcard it'd still fit into 100MB.
Ubiquitous, but not universal and uninterrupted. And you can pretty much guarantee that the time its needed the most will be the time that it's not available.
I should add for the avoidance of doubt that the rationale I gave above is the one that has been given by TfL in the past. Personally I completely accept that it was reasonable at the time, but can agree now that its standing has been changed somewhat by advances in connectivity over time.

EDIT: I see @Mojo has expanded on the rationale in #25.

Nevertheless, as @najaB notes, those advances haven't yet delivered uninterrupted connectivity so you'd have to implement the full-list-carried-on-device part of the proposal anyway. Technically I don't think that this is anywhere near the challenge now as it would have been even ten years ago, given that mobile devices have far more storage space and processing power now, but it still introduces security concerns in maintaining and distributing the Railcard-associated-card list. These might be easy to overcome, or they might not - I don't have experience sufficient to say.

Alternately, you don't keep the list on inspection devices and just accept that whenever an inspector's device cannot make live queries against the database passengers will be able to present discounted cards without being verified. I wouldn't want to hazard a guess as to the rate at which that would occur, but there is an argument that accepting a certain amount of 'leakage' is still cheaper than implementing the watertight solution.

Let's not forget as well that even registering the Railcard against a contactless card will need architecture that doesn't exist (AFAIK) yet - if it's done via TVMs as per the current Oyster process then it will require the TVMs be able to connect and write to the accounts database, as opposed to simply writing to the Oyster as they do now.

Simple fix: Require customers to wait 1 day before travelling for their Railcard discount to take effect.

You can refresh the bloom filter at least once a day, I refuse to believe a revenue inspector can be outside of mobile data coverage for an uninterrupted 24 hours.
And if I want to travel today?
This would also be a question of acceptable leakage. If you design the system to be at the watertight end of things, you'd simply say "too bad - the discount takes effect at 0430 on the day after it's added to the card" because that unquestionably gives time for the on-device list to be updated by the time RPIs are clocking-on the next morning. At the other end, you'd allow same-day travel on the grounds that the list will probably be updated much sooner than the next morning, and that even if it isn't the maximum window of opportunity for exploitation of an improperly-transferred discount will never exceed 24 hours.
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
30,691
Location
Scotland
Let's not forget as well that even registering the Railcard against a contactless card will need architecture that doesn't exist (AFAIK) yet - if it's done via TVMs as per the current Oyster process then it will require the TVMs be able to connect and write to the accounts database, as opposed to simply writing to the Oyster as they do now.
Also, would the railcard be linked to a single contactless payment card? Or would it be linked to multiple devices? With railcards linked to a single Oyster card you can be sure that it's only being used by one person at a time, but if it's linked to more than one contactless payment device? Even if the uses don't overlap, it's still possible for more than one person to gain benefit of a single railcard discount without them having to meet up to transfer the card.
 

XAM2175

Established Member
Joined
8 Jun 2016
Messages
3,469
Location
Glasgow
Also, would the railcard be linked to a single contactless payment card? Or would it be linked to multiple devices? With railcards linked to a single Oyster card you can be sure that it's only being used by one person at a time, but if it's linked to more than one contactless payment device? Even if the uses don't overlap, it's still possible for more than one person to gain benefit of a single railcard discount without them having to meet up to transfer the card.
Unless I'm overlooking something, there's very little risk to TfL in registering the discount against multiple cards (physical or virtual) so long as the person using any of those cards for travel can present a valid Railcard at the time of inspection - but it would definitely affect the calculations that inform acceptable leakage decisions (so if you allow discounted travel on the same day as registering the discount, you might impose a limit of, say, two card registrations per day to reduce exposure to exploitation).
 

najaB

Veteran Member
Joined
28 Aug 2011
Messages
30,691
Location
Scotland
Unless I'm overlooking something, there's very little risk to TfL in registering the discount against multiple cards (physical or virtual) so long as the person using any of those cards for travel can present a valid Railcard at the time of inspection - but it would definitely affect the calculations that inform acceptable leakage decisions (so if you allow discounted travel on the same day as registering the discount, you might impose a limit of, say, two card registrations per day to reduce exposure to exploitation).
If you still need to present a physical railcard then I agree. I thought the idea was to load a digital railcard into the Oyster account and automatically apply the discount without a card ever needing to be presented. If I've misunderstood then please ignore my posts on the matter.
 

MikeWh

Established Member
Associate Staff
Senior Fares Advisor
Joined
15 Jun 2010
Messages
7,865
Location
Crayford
If you still need to present a physical railcard then I agree. I thought the idea was to load a digital railcard into the Oyster account and automatically apply the discount without a card ever needing to be presented. If I've misunderstood then please ignore my posts on the matter.
That was my understanding too. A TfL account can have unlimited Oyster and CPCs attached to it. I have 3 CPCs attached to mine in case something goes wrong and I need to use another card. If I had visitors who didn't have their own cards then I could lend one to them. In 6 months I'll be entitled to a Railcard again, but visitors might not be. It's not inconceivable that I may wish to pay for my friend's travel which is another reason to lend a card.
 
Status
Not open for further replies.

Top