Precursor

Early electronic smartcard ticket technology was developed in the 1980s, and the first smartcard was tested by London Transport on bus route 212 from Chingford to Walthamstow in 1992. The trial showed that the technology was possible and that it would reduce boarding times.^[11][12] In February 1994, the "Smartcard" or "Smart Photocard" was launched and trialled in Harrow on 21 routes. Advertised as "the new passport to Harrow’s buses", the trial was the largest of its kind in the world, costing £2 million and resulting in almost 18,000 photocards issued to the Harrow public. It lasted until December 1995 and was a success, proving that it reduces boarding times, is easy to use, and is able to record entry and exit stops and calculate the corresponding fare fee, i.e. pay as you go.

However, the Upass smartcard of the South Korean capital Seoul would eventually be the first in the world to roll out this sort of technology, at the end of 1995, eight years before London would as the "Oyster card".^[13] In the UK, the first smartcard publicly rolled out was the BusCard in the city of Nottingham in 2000.^[14]

Operator

The Oyster card was set up under a Private Finance Initiative (PFI) contract between Transport for London (TfL) and TranSys, a consortium of suppliers that included EDS and Cubic Transportation Systems (responsible for day-to-day management) and Fujitsu and WS Atkins (shareholders with no active involvement).^[15] The £100 million contract was signed in 1998 for a term of 17 years until 2015 at a total cost of £1.1 billion.^[16]

In August 2008, TfL decided to exercise a break option in the contract to terminate it in 2010, five years early. This followed a number of technical failures.^[17] TfL stated that the contractual break was to reduce costs, not connected to the system failures.^[18] In November 2008 a new contract was announced between TfL and Cubic and EDS for two of the original consortium shareholders to run the system from 2010 until 2013.^[19]

Brand

The Oyster name was agreed on after a lengthy period of research managed by TranSys and agreed by TfL. Two other names were considered^[20] and "Oyster" was chosen as a fresh approach that was not directly linked to transport, ticketing or London. Other proposed names were "Pulse" and "Gem". According to Andrew McCrum, now of Appella brand name consultants, who was brought in to find a name by Saatchi and Saatchi Design (contracted by TranSys), "Oyster was conceived ... because of the metaphorical implications of security and value in the hard bivalve shell and the concealed pearl. Its associations with London through Thames estuary oyster beds and the major relevance of the popular idiom "the world is your oyster" were also significant factors in its selection".^[21]

The intellectual property rights to the Oyster brand originally belonged to TranSys. Following the renegotiation of the operating contract in 2008, TfL sought to retain the right to use the Oyster brand after the termination of its partnership with Transys,^[19][22] eventually acquiring the rights to the brand in 2010 at a cost of £1 million.^[23]

Technology

A damaged Oyster card, revealing the microchip in the lower right corner and the aerial running around the perimeter of the card.

The Oyster card has a claimed proximity range of about 80 mm (3 inches). The card operates as a RFID system and is compatible with ISO/IEC 14443 types A and B. Oyster readers can also read other types of cards including Cubic Transportation Systems' Go cards. From its inception until January 2010, Oyster cards were based on NXP/Philips' MIFARE Classic 1k chips provided by Giesecke & Devrient, Gemalto and SchlumbergerSema.^[24] All new Oyster cards have used MIFARE DESFire EV1 chips since December 2009. From February 2010, MIFARE Classic-based Oyster cards were no longer issued.^[25] MIFARE DESFire cards are now widely used as transport smartcards.

MIFARE Classic chips, on which the original Oyster card was based, are hard-wired logic smartcards, meaning that they have limited computing power designed for a specific task. The MIFARE DESFire chips used on the new Oyster card are CPUs with much more sophisticated security features and more complex computation power. They are activated only when they are in an electromagnetic field compatible with ISO/IEC 14443 type A, provided by Oyster readers. The readers read information from the cards, calculate whether to allow travel, assess any fare payable and write back information to the card. Some basic information about the MIFARE Classic or MIFARE DESFire chip can be read by any ISO/IEC 14443 type A compatible reader, but Oyster-specific information cannot be read without access to the encryption used for the Oyster system. While it has been suggested that a good reader could read personal details from a distance, there has been no evidence of anyone being able to decrypt Oyster information. By design the cards do not carry any personal information. Aluminium shielding has been suggested to prevent any personal data from being read.^[26]

Oyster uses a distributed settlement framework. All transactions are settled between the card and reader alone. Readers transmit the transactions to the back office in batches but there is no need for this to be done in real time. The back office acts mainly as a record of transactions that have been completed between cards and readers. This provides a high degree of resilience.

In 2008, a fashion caught on for removing the RFID chip from Oyster cards and attaching it to wrist watches and bracelets. This allowed commuters to pass through the gates by "swiping" their hand without the need to take out a proper card. Although the RFID chips were charged in the normal way and no fare evasion was involved, TfL disapproved of the practice and threatened to fine anyone not carrying a full undamaged card,^[27] although it is not clear what the actual offence would be, were a case to be brought.

Architecture

The Oyster system is based on a closed, proprietary architecture from Cubic Transportation Systems. The card readers were developed entirely by Cubic, whereas development of the back office systems was started by Fujitsu and completed by Cubic. The system has the capability to interface with equipment or services provided by other suppliers. The Oyster website is not part of the closed system but interfaces with it. Similarly, Oyster readers are now embedded into ticket machines produced by Shere and Scheidt and Bachmann on the national rail network.

The back of a second generation card

In early 2007, TfL and Deloitte worked to migrate the on-line payment systems to a more open architecture, using a number of open source components such as Linux, to resolve issues of lock-in costs, updates, incorporation of new security standards of PCI DSS, non-scalability, low and inconsistent quality of service, and slower response time to business changes.^[28]

Registration and protection

The back of a first-generation Oyster card

Oyster cards can be registered, providing protection in case of loss or theft. Registration can be done online after the card has been used for a journey. It can also be commenced at a London Underground station, an Oyster Ticket Stop (shop) or a Travel Information Centre; for this, the customer has to supply a security password and their postcode, which must then be cited when completing the registration online. Registration enables the customer to buy any product for the card and to have an after-sales service, and it protects against theft or loss.

Sales

Oyster card vending machine, installed at London Bridge station in December 2006. All machines of this design have been phased out.

Oyster cards can be purchased from a number of different outlets in the London area:

• Ticket machines at London Underground stations, which accept banknotes, coins, and credit and debit cards.
• London Overground & TfL Rail ticket offices
• Online, using the TfL website
• Through the TfL app
• Selected National Rail stations, some of which are also served by London Underground
• Travel Information Centres
• About 4,000 Oyster Ticket Stop agents (usually newsagent's shops)
• By telephone sales from TfL.^[29]

As well as the £7 fee for the card, a minimum purchase of £5 credit or a week Travelcard or Bus & Tram Pass is necessary at point of issue.

Visitor Oyster cards can be obtained from Visit Britain outlets around the world, and from other transport operators, such as EasyJet and Gatwick Express, and online and from any ticket office. However, these limited-functionality cards cannot be registered. Any remaining credit on the card is refundable upon return of the card; the £5 price of the card is not refunded.^[30]

Oyster cards were initially free, but a refundable deposit of £3 was subsequently introduced,^[31] increased to £5 for a refundable Oyster card in January 2011,.^[32] Any deposit and unused credit are refundable by posting the card to TfL; however, refunds are paid only by pounds sterling cheque, bank transfer to a UK bank account, credit to another Oyster card, or a TfL web account voucher, and refunds of over £15 require the customer to provide proof of identity and address.^[33] Refunds of up to £10 in credit plus the deposit may alternatively be claimed at London Underground ticket machines, which will pay the refund in cash.^[34] Even though the £5 deposit is officially for the card itself, the ticket machine has no facility for relieving the customer of the card who departs the transaction still in possession of a (now useless) Oyster card. On cards issued since February 2020, the £5 deposit became a card fee and will be repaid as credit to the card on the first transaction made more than a year after issue. From September 2022, the card issue fee went up to £7 and this is no longer refundable.^[35]

Oyster cards can be registered via the TfL website, or with staff assistance at London Underground ticket machines. Unregistered cards can only be loaded with credit to use at adult pay as you go rates, and adult 7 day Travelcards.^[36]

Ticket vending machines on most National Rail stations will top-up Oyster cards and sell tickets that can be loaded on to Oyster. New Oyster cards are not available at most National Rail stations.^[37] At several main line termini, TfL runs Travel Information Centres, which do sell Oyster.

Reporting

Oyster Travel Statement

Touch-screen ticket machines report the last eight journeys and last top-up amount. The balance is displayed on some Underground barriers at the end of journeys that have caused a debit from the balance, and can also be requested at newsagents and National Rail stations that provide a top-up facility.

Oyster Online service can also deliver regular Travel Statements via email.

A complete 8-week 'touch' history can be requested from TfL: for registered and protected Oyster cards, TfL can provide the history for the previous 8 weeks, but no further back. Oyster online also displays up to 8 weeks of journey history.

Touching in and out

Travellers touch the card on a distinctive yellow circular reader (a Tri-Reader, developed by Cubic Transportation Systems) on the automated barriers at London Underground stations to touch in and touch out at the start and end of a journey. Physical contact is not necessary, but the range of the reader is only a few millimetres. Tram stops have readers on the platforms, and buses also have readers on the driver/conductor's ticket machine, and on these modes passengers must touch their card to the reader at the start of their journey only, with the exception of tram journeys to Wimbledon station, where trams arrive within the ticket-gates and as such a touch-out is necessary to leave the station. At stations without barriers, such as most Docklands Light Railway stations, passengers must touch their card on a reader at both the beginning and end of their journey if they wish to avoid being charged the maximum fare for an unresolved journey. Such a step is not needed if transferring between trains within a station when using the same card for the full journey, but if changing between Oyster and a separate National Rail ticket, the Oyster card must be touched in/out at the interchange station as appropriate.

Season tickets

Oyster cards can be used to store season tickets of both travelcards and bus passes (of one week or more), and a Pay-as-you-go balance.

An Oyster card can hold up to three season tickets at the same time. Season tickets are Bus & Tram Passes or Travelcards lasting 7 days, 1 month, or any duration up to one year (annual).

Travelcards are valid on all Underground, Overground, DLR, bus, tram and national rail services within the zones purchased. See the main article for a fuller explanation of Travelcards. Tube, DLR and London Overground Travelcards may be used on buses in all zones. Trams may also be used if the travelcard includes Zones 3, 4, 5 or 6.^[38]

Although TfL asks all Oyster users to tap their card at entry/exit points of their journey, in practice Travelcard holders only need to "touch in" and "touch out" to operate ticket barriers or because they intend to travel outside the zones for which their Travelcard is valid. As long as the Travelcard holder stays within their permitted zones no fare will be deducted from the pay-as-you-go funds on the card. The Oyster system checks that the Travelcard is valid in the zones it is being used in.

Renewals

Oyster card top-up machine at IFS Cloud Royal Docks

Oyster card Travelcards can be renewed at the normal sales points and ticket machines at London Underground or London Overground stations, Oyster Ticket Stop agents, or some National Rail stations. Travelcards can also be renewed online via the Oystercard website, or by telephone sales from TfL. Alternatively a user can choose to automatically add either £20 or £40 every time the balance on the card falls below £20, with payment charged to a registered credit or debit card. Online purchases can be collected at any Oyster touch point (including buses, but not including ticket machines) 30 minutes after purchase; the previous requirement to nominate a station at which to collect the top-up and wait until the next day has been removed. The touch will start (or, as applicable, end) a journey in the normal way, and may result in a charge to the card.

Pay-as-you-go

In addition to holding Travelcards and bus passes, Oyster cards can also be used as stored-value cards, holding electronic funds of money. Amounts are deducted from the card each time it is used, and the funds can be "recharged" when required. The maximum value that an Oyster card may hold is £90. This system is known as "pay as you go" (abbreviated PAYG), because instead of holding a season ticket, the user only pays at the point of use.

When Oyster cards were introduced, the PAYG system was initially named "pre pay", and this name is still sometimes used by National Rail. TfL officially refers to the system as "pay as you go" in all publicity.

The validity of PAYG has a more complex history as it has only been gradually accepted by transport operators independent of TfL. Additionally, the use of PAYG differs across the various modes of transport in London, and passengers are sometimes required to follow different procedures to pay for their journey correctly.

It is possible to have a negative pay-as-you-go balance after completing a journey, but this will prevent the card from being used (even if it is loaded with a valid Travelcard) until the card is topped up.

Underground and DLR

London Underground ticket barriers with yellow Oyster readers

Oyster card pay-as-you-go users must "touch in" at the start of a journey by London Underground or DLR, and "touch out" again at the end. The Oyster card readers automatically calculate the correct fare based on the start and end points of the journey and deduct that fare from the Oyster card. Pay-as-you-go funds are also used to cover any additional fares due from season ticket holders who have travelled outside the valid zones of their season ticket (see Travelcards above).

Passengers enter or exit most London Underground stations through ticket barriers which are operated by scanning an Oyster card or inserting a valid ticket. Some tube stations (such as those at National Rail interchanges) and DLR stations have standalone validators with no barriers. In both instances, pay-as-you-go users are required to touch in and out.

Buses

Oyster validators are placed at most entrances on London buses.

Users must touch the Oyster card only once at the point of boarding: as London buses have a flat fare of £1.75 (which allows for unlimited bus and tram journeys started within 62 minutes from the point of touching in^[40]), there is no need to calculate an end point of the journey.

From July 2016, cash was no longer accepted on London Buses, with TfL heavily promoting the use of a contactless card or Oyster card.^[41] All major contactless cards are accepted which carry the 'contactless symbol'.

As London buses do not accept cash payments, TfL introduced a "one more journey" incentive on Oyster cards.^[42] This meant that customers are able to take a bus if their cards have £0 or more. Doing so may result in a negative balance, but the card can be topped up at a later date. When using the 'one more journey' feature, customers receive an emergency fare advice slip to acknowledge that the Oyster 'One More Journey' feature has been used and to remind them that their card needs to be topped up before another journey can be made.^[43] It is estimated that by eliminating cash from buses, TfL will save £103m by the year 2023,^[43] which will be reinvested into the capital.

Some London bus routes cross outside the Greater London boundary before reaching their terminus. Pay-as-you-go users are permitted to travel the full length of these route on buses operated as part of the London Bus network, even to destinations some distance outside Greater London.

Trams

An Oyster validator at a tram stop

London's trams operate on the same fare structure as buses; the rules are similar, and users with pre-pay must touch the Oyster card only once at the point of boarding. Transfers between trams and buses are free within 62 minutes (publicly stated as "one hour") of the first touch-in. Passengers should not touch out at the end of the journey, although in practice, no charge is usually made to cards should this happen as it would come under the free transfer. Users with Travelcards valid for the Tramlink zones need not touch in unless travelling to Wimbledon with a Travelcard not valid in zone 3.

A more complex arrangement exists at Wimbledon station; tram passengers starting their journey there must pass through ticket gates in order to reach the tram platform, and therefore need to touch their Oyster card to open the barriers. They must then touch their Oyster card once again on the card reader on the Tramlink platform to confirm their journey as a tram passenger. Tram passengers arriving in Wimbledon must not touch out on the card reader on the Tramlink platform, but must touch-out to exit via the station gates. If the card is touched on the platform, the touch-out at the gate would be seen as a touch-in and cause the maximum fare to be charged to the card.^[44]

River

A Thames Clipper river bus service

An Oyster card reader at a riverbus pier

Passengers boarding a Thames Clippers riverbus service must tap their Oyster card on the reader situated on the pier before boarding. Thames Clippers operates a pay-before-boarding policy.^[45]

National Rail

National Rail ticket barriers with yellow Oyster readers

Standalone Oyster readers provided at interchange stations between National Rail and the Tube

As with Underground and DLR journeys, Oyster PAYG users on National Rail must tap their card at the start and end of the journey to pay the correct fare. PAYG funds may also be used to cover any additional fares due from season ticket holders who have travelled outside the valid zones of their season ticket (see Travelcards above).

Many large National Rail stations in London have Oystercard-compatible barriers. At other smaller stations, users must touch the card on a standalone validator.

Oyster photocards

Oyster photocards, with an image of the authorised user on the card front, are issued to members of groups eligible for free or discounted travel. The cards are encoded to offer discounted fares and are available for students in full-time education (30% off season tickets), 16+ cards (half the adult-rate for single journeys on the Underground, London Overground, DLR and a limited number of National Rail services, discounted period Travelcards, free travel on buses and trams for students that live and attend full-time education in London) and for children under 16 years old (free travel on buses and trams and discounted single fares on the Underground, London Overground, DLR and most National Rail services). A 'Bus & Tram' Discount Card is specifically given to disadvantaged and 'unwaged' groups, primarily those on 'Job Seekers Allowance', 'Employment Support Allowance' and receivers of a variety of disabilities allowances, at half-fare rates for bus and tram services only; these cards simply charge the full rate on journeys not included in the discount scheme.

Oyster and credit card

The OnePulse card

A credit card variant of the Oyster card called OnePulse was launched by Barclaycard in September 2007, combining standard Oyster card functionality with Visa credit card facilities. It incorporated contactless payment technology, allowing most transactions up to £20 to be carried out without the need to enter a PIN (unlike the Chip and PIN system).^[56]

In 2005, Transport for London shortlisted two financial services suppliers, Barclaycard and American Express, to add e-money payment capability to the Oyster card. Barclaycard was selected in December 2006 to supply the card,^[57] but the project was then temporarily shelved.^[58] The OnePulse card was later launched using a combination of Oyster and Visa, but with no e-money functionality.

The OnePulse card was withdrawn from use and ceased to be functional on 30 June 2014, due to technological changes; customers had their OnePulse card replaced by the Freedom Rewards credit card.^[59]

TfL services

Oyster is operated by Transport for London and has been valid on all London Underground, London Buses, DLR and London Tramlink services since its launch in 2003, and on all London Overground services since their start of operation. However, Oyster is not accepted on Elizabeth line west of West Drayton towards Reading, which is the only TfL service not accepting Oyster.

National Rail

The introduction of Oyster pay as you go on the National Rail commuter rail network in London was phased in gradually over a period of about six years (see Roll-out history). Since January 2010, PAYG has been valid on all London suburban rail services which accept Travelcards. Additionally, PAYG may be used at a selected number of stations which lie just outside the zones. New maps were issued in January 2010 which illustrates where PAYG is now valid.^[60][61]

Certain limitations remain on National Rail, however.

Heathrow Express accepts Oyster pay as you go since 19 February 2019.^[62]

In November 2007, the metro routes operated by Silverlink were brought under the control of TfL and operated under the brand name London Overground. From the first day of operation, Oyster PAYG became valid on all Overground routes.^[63]

London Oyster Cards and contactless cards will be accepted on many Southern, Gatwick Express and Thameslink services in early 2016. These include to Gatwick Airport station and five other Surrey railway stations, as well as to Luton Airport.^[64][65][66]

London River Services

Since 23 November 2009, Oyster PAYG has been valid on London River Services boats operated by Thames Clippers only.^[45] Oyster cards are accepted for all Thames Clippers scheduled services, the DoubleTree Docklands ferry, the "Tate to Tate" service and the O2 Express. Discounts on standard fares are offered to Oyster cardholders, except on the O2 Express. The daily price capping guarantee does not apply to journeys made on Thames Clippers.^[67]

London Cable Car

Oyster card holders (PAYG, Travelcard or Freedom Pass) receive discounts on the London Cable Car across the River Thames between Greenwich and the Royal Docks, which opened in June 2012. Like London River Services, the cable car is a privately funded concern and is not fully integrated into TfL's ticketing system.^[68] To encourage use of the cable car as a commuter service, substantial discounts are offered with a "frequent flyer" ticket which allows 10 journeys within 12 months.^[69]

Adult single fares

Cash is no longer accepted on London's buses and trams and, in order to encourage passengers to use Oyster or contactless, cash fares for tubes and trains are generally much more expensive than PAYG fares. A contactless debit or credit card can be used in place of an Oyster card at the same fare.

The single Oyster fare for a bus or tram journey is £1.75, although the Hopper fare rules allow unlimited bus and tram journeys within one hour of first touching in for no additional cost. (To allow for disputes over clock settings, the system uses a time limit of 62 minutes.) Passengers need to touch in using the same card on all the bus and tram journeys made and any free fares are applied automatically.^[71]

Using PAYG, a single trip on the tube within zone 1 costs £2.80 peak / £2.70 off-peak (compared to £6.70 if paid by cash). Tube journeys within any other single zone cost £1.90 at peak times and £1.80 off peak (£6.70 for cash at any time).^[70] Journeys in multiple zones are progressively more expensive.^[70]

However, even for journeys passing through the same zones, the price may be different depending on the actual line(s) used. For example, a journey from Willesden Junction to Wimbledon has 5 different routes, 3 of them involving travel between zones 1-3 and 2 of them within zones 2-3 only, defined in the route database.^[70] If travel is made by changing at West Brompton onto the District line by touching the pink reader there, the fare charged is only £2.10 peak / £1.90 off-peak, while if a touch is not made there, travel is assumed to be via Clapham Junction onto the South Western Railway which is on a more expensive fare scale than the tube even though the trips are within the same zones. Similarly, travelling via zone 1 is more expensive if a change onto the South Western Railway is made at London Waterloo compared to using the tube all the way from Euston via Earl's Court.

Travel to Heathrow Airport via Elizabeth line is more expensive than going via the tube even though both the tube and the Elizabeth line stations are in zone 6.

For every possible journey, there is a default route, possibly with other routes distinguished by intermediate touches, in the fare database. Each route has an associated "zones travelled" label which are the zones assumed to be travelled through. When touching out at a reader, the system looks up the appropriate route from the database according to the touches, which is the default route if no intermediate touches are made or if they don't match any of the alternative routes, to charge the correct fare, and to record the assumed zones travelled into the card for capping purpose.

The zoned fare system under which Oyster operates inevitably gives rise to some quirks in the fares charged. A 21 stop journey between Stratford and Clapham Junction on the overground is charged at £1.90 at peak times (£1.80 off peak) whereas a 1 stop journey between Whitechapel and Shoreditch High Street on the overground costs £2.80 peak or £2.70 off-peak.^[70] This occurs because Whitechapel to Shoreditch High Street uses zone 1 and zone 2, as Shoreditch High Street is in zone 1 only, whereas the entire Stratford to Clapham Junction line runs in zone 2 only.^[72] The cash fare is £6.70 in both cases and at all times.^[70] Similar anomalies are a feature of zoned fare systems worldwide.

Fare capping

A 'capping' system was introduced on 27 February 2005, which means that an Oyster card will be charged no more than the nearest equivalent Day Travelcard for a day's travel, if penalty fares are not incurred. The daily cap is £8.10 within zones 1-2 and £14.90 within zones 1–6, provided no maximum fares are incurred for failure to touch in or out, or for touching in or out at the same station.^[73] A lower cap of £5.25 applies if the day's journeys are restricted to buses and trams only.^[74]

There are 3 different caps in use: all-day cap (valid from 04:30 weekdays to 04:29 the next day on all rail, tram and bus services), off-peak cap (valid from 09:30 weekdays / 04:30 weekends to 04:29 the next day on all rail, tram and bus services) and bus & tram cap (valid from 04:30 to 04:29 the next day on buses and trams only). For both the all-day cap and off-peak cap, the respective zones travelled are recorded onto the card.

The Oyster system supports up to 15 zones. Stations which are not officially in zones 1-9 are allocated to the unpublicised zones, denoted A-E in hexadecimal (or 10-14 in denary), such as Watford Junction.

Because of how the price capping works, it can sometimes result in overcharging compared to using multiple Oyster cards. For example, if one takes a journey from zone 6 all the way to zone 1, then takes multiple journeys within zones 1-2, the system will charge for the journeys until the zone 1-6 cap is reached even though it may be cheaper to charge a zone 1-2 cap combined with a single fare from zone 6 because zone 1-6 travel is already recorded on the card. Contactless users don't suffer from this problem as fare calculation is done at the backend after the day of travel, where the cheapest combination of fares is charged. TfL is working on a similar system for Oyster as well such that overcharged fares may be refunded afterwards.^[75] The complex interaction between single fares and the various caps may also mean that, by deliberately taking an extra bus journey, the total fare for the day may be reduced.^[76]

Price capping does not apply to PAYG fares on Heathrow Express, Gatwick Express, London River Services boats and on Southeastern high speed train services.^[67]

Travelcards

Season Travelcards within zones 1-9, Watford Junction, Hertford East / Broxbourne, and Shenfield can be loaded onto an Oyster card. For journeys totally within the zones covered by the Travelcard, no additional fare is deducted. However, if the default route is assumed to go through zone 1, and the Travelcard doesn't cover zone 1, the user must tell the system that zone 1 is avoided by touching a pink reader when changing trains using a route which doesn't pass through zone 1, otherwise an additional zone 1 fare is deducted. Because of how the system work, an Oyster Travelcard covering Hertford East / Broxbourne can also be used at Watford Junction, and an Oyster Travelcard covering Shenfield can also be used at Watford Junction, Hertford East and Broxbourne,^[77] as internally Watford Junction is in zone 10, Hertford East and Broxbourne is in zone 11 and Shenfield is in zone 12. This extra availability doesn't extend to paper Travelcards.

For journeys partially within the Travelcard coverage, an extension fare, corresponding to the extra zones used, is charged from the PAYG balance. If the PAYG balance is negative, the Oyster card can no longer be used for travel even within the zones covered until it is restored to zero or above by topping up.

Railcard discount

Holders of Disabled Persons, HM Forces, Senior, 16–25, 26-30 National Rail Railcards and Annual Gold Cards (as of 23 May 2010) receive a 34% reduction in the off-peak PAYG fares and price cap; Railcard discounts can be loaded on at London Underground ticket machines (with help from a member of staff).

Bus and tram discount

On 20 August 2007, a 'Bus and Tram Discount photocard' was launched for London Oyster card users who received Income Support. It allows cardholders to pay £0.75 for a single bus journey (capped at £2.25 per day), and to buy half price period bus passes.

This was originally the result of a deal between Transport for London and Petróleos de Venezuela to provide fuel for London Buses at a 20% discount. In return Transport for London agreed to open an office in the Venezuelan capital Caracas to offer expertise on town planning, tourism, public protection and environmental issues.^[78] The deal with Venezuela was ended by Mayor Boris Johnson shortly after he took office, and the Bus and Tram Discount photocard scheme closed to new applications on 20 August 2008; Johnson said that "TfL will honour the discount [on existing cards] until the six-month time periods on cards have run out".^[79]

The Bus and Tram Discount Scheme reopened on 2 January 2009, this time funded by London fare payers. The scheme has been extended to people receiving Employment and Support Allowance (ESA) and to those receiving Jobseeker's Allowance for 13 weeks or more.

River Bus discounts

Boats operated by Thames Clippers offer a 10% discount on standard fares to Oyster PAYG users, except on their O2 Express service, and a 1/3 discount to passengers carrying Oyster cards which have been loaded with a valid period Travelcard.^[67]

Minimum and maximum fare

In order to prevent "misuse" by a stated 2% of passengers, from 19 November 2006 pay as you go users are automatically charged the "maximum Oyster fare" for a journey on that network when they touch in. Depending on the journey made, the difference between this maximum fare and the actual fare due is automatically refunded to the user's Oyster card upon touching out. The maximum fare is automatically charged to a passenger who touches out without having first touched in. Two maximum fares are charged (one for touching in, one for touching out) if a passenger touches in at a station, waits for over twenty minutes, and then touches out at the same station, because the system assumes that the passenger has been able to travel to another station in that time, taking no account of situations where there are severe delays.

Users must touch in and out even if the ticket barriers are open. At stations where Oyster is accepted but that do not have ticket barriers, an Oyster validator will be provided for the purposes of touching in and out. The maximum Oyster fare applies even if the daily price cap has been reached as this does not count towards the cap.

The system allows starting a journey if the balance of the card is at least the minimum fare from the station, which may be 0 if the card reaches a cap or if the station is within the zones covered by a Travelcard. However the maximum fare is deducted upon entry which may bring the balance to negative at this point.^[80]

Maximum Oyster fares may be contested by telephone to the Oyster helpline on 0343 222 1234^[81] or via email. This involves providing the Oyster card number and the relevant journey details; further journeys appearing on the card are helpful to validate the user's claim.

If the claim is accepted then the maximum Oyster fare minus the cost of the journey will be refunded. This is credited to the card the next time it is used on a journey. The only way to collect a refund is as part of an actual journey, otherwise a further maximum fare is charged. This is because when the passenger touches the reader with their Oyster card, not only will the refund go on to the card, but a new journey will start.

Refunds become available to collect within 30 minutes. There is no longer a requirement to nominate a specific station from which to collect the refund.

Customers claiming a refund must do so within 8 weeks of the overcharge.

Oyster users who do not touch in before making a journey may be liable to pay a penalty fare (£80) and/or reported for prosecution if caught by a revenue protection inspector.

Refunds for delayed journeys

Commuters who were delayed 15 minutes or more on the Tube & DLR,^[82] and 30 minutes or more on London Overground & TfL Rail,^[83] are eligible to claim a refund for the cost of their journey. Commuters with Travelcards that do not pay for individual journeys will be refunded the Pay As You Go price of that single delayed journey.^[84] Customers wishing to claim these refunds must create an online TfL account, and then either manually claim online each time they are delayed, or use the free Train Reeclaim tool which automatically detects delayed TfL journeys and claims a refund on behalf of the commuter for each one.^[85]

Roll-out on National Rail

Until January 2010, many rail operators did not accept Oyster PAYG and posted warning notices inside their stations.

The National Rail network is mostly outside the control of Transport for London, and passenger services are run by number of independent rail companies. Because of this, acceptance of Oyster PAYG on National Rail services was subject to the policy of each individual company and the roll-out of PAYG was much slower than on TfL services.^[94] For the first six years of Oyster, rollout on National Rail was gradual and uneven, with validity limited to specific lines and stations.

Several rail companies have accepted London Underground single fares because they duplicate London Underground routes, and they adopted the Oyster PAYG on those sections of the line which run alongside the Underground. When TfL took over the former Silverlink Metro railway lines, PAYG was rolled out on the first day of operation of London Overground. As a consequence, some rail operators whose services run parallel to London Overground lines were forced to accept PAYG,^[95] although only after some initial hesitation.^[96][97]

Examples of these services include London Midland trains from Watford Junction to London Euston and Southern trains to Clapham Junction.

The growing PAYG rail network 2006–08: more stations added

The process of persuading the various rail firms involved a long process of negotiation between the London Mayors and train operating companies. In 2005 Ken Livingstone (then Mayor of London) began a process of trying to persuade National Rail train operating companies to allow Oyster PAYG on all of their services within London, but a dispute about ticketing prevented this plan from going ahead.^[98] After further negotiations, Transport for London offered to fund the train operating companies with £20m to provide Oyster facilities in London stations; this resulted in an outline agreement to introduce PAYG acceptance across the entire London rail network.^[99]

TfL announced a National Rail rollout date of May 2009,^[100] but negotiation with the private rail firms continued to fail and the rollout was delayed to 2010. Oyster readers were installed at many National Rail stations across London, but they remained covered up and not in use.^[101] In November 2009 it was finally confirmed that PAYG would be valid on National Rail from January 2010.^[90] The rollout was accompanied by the introduction of a new system of Oyster Extension Permits to allow travelcard holders to travel outside their designated zones on National Rail. This system was introduced to address the revenue protection concerns of the rail companies, but it was criticised for its complexity,^[102][103] and was abolished on 22 May 2011.^[39]

Beyond London

Since January 2010, Oyster PAYG is valid at c2c stations Purfleet, Ockendon, Chafford Hundred and Grays in Thurrock (Essex).

On 2 January 2013, Oyster PAYG was extended to Shenfield (a terminus of the Elizabeth line) and Broxbourne by Abellio Greater Anglia.^[106][107]

With regard to London's airports, TfL and BAA studied acceptance of Oyster Pay As You Go on BAA's Heathrow Express service and the Southern-operated Gatwick Express service in 2006, but BAA decided not to go ahead.^[108] However, Oyster has been valid to Gatwick Airport on both the Gatwick Express and Southern Rail and Thameslink services since January 2016.^[109]

Oyster was extended to Hertford East when London Overground took over suburban services previously operated by Greater Anglia in May 2015.

Oyster was extended to Epsom, Hertford North, Potters Bar and Radlett in Summer 2019.

There are proposals to extend the PAYG service to the remainder of the c2c network (all routes to Southend and Shoeburyness), Thameslink as far as Sevenoaks and Southern / GWR to Reigate.^[110]

Contactless payment

In 2014, Transport for London became the first public transport provider in the world to accept payment from contactless bank cards.^[9] TfL first started accepting contactless debit and credit cards on London Buses on 13 December 2012,^[111] expanding to the Underground, Tram and the Docklands Light Railway in September 2014.^[112] Since 2016, contactless payment can also take place using contactless-enabled mobile devices such as phones and smartwatches, using Apple Pay,^[113] Google Pay and Samsung Pay.^[114]

TfL designed and coded the contactless payment system in-house, at a cost of £11m, after realising existing commercial solutions were inflexible or too focused on retail use.^[9] Since the launch of contactless payment in 2012, over 500 million journeys have been made, using over 12 million contactless bank cards.^[10] Consequently, TfL is now one of Europe's largest contactless merchants, with around 1 in 10 contactless transactions in the UK taking place on the TfL network.^[10]

In 2016, TfL licensed their contactless payment system to Cubic, the original developers of the Oyster card, allowing the technology to be sold to other transport providers worldwide.^[10] In 2017, licensing deals were signed with New York City,^[115] New South Wales^[116] and Boston.^[117]

The same requirement to touch in and out on underground services applies to contactless cards. The same price capping that applies to the use of Oyster cards applies to the use of contactless cards (provided the same card is used for the day's journeys). The fare paid every day is settled with the bank and appears on the debit or credit card statement. Detailed usage data is written to Transport for London's systems and is available for customers who register their contactless cards with Transport for London. Unlike an Oyster card, a contactless card does not store credit (beyond the holder's credit limit) and there is no need or facility to add credit to the card.

An Oyster card can have a longer term "season" ticket loaded onto it (either at a ticket office or on line). Such a ticket can start on any day and be valid for a minimum of seven days and a maximum of one year. Unlike an Oyster card, a contactless card can automatically apply a seven-day travel card rate. If the card is regularly used between any Monday to Sunday period, an automatic cap is applied. The seven-day period is fixed at Monday to Sunday, it cannot be any seven-day period, unlike a seven-day ticket applied to an Oyster card. There is currently no automatic cap for longer periods.^[118]

Since the Oyster readers cannot write to a contactless card, the reader when touching out is unable to display the fare charged for the journey, as the card does not have the starting point stored in it. This is calculated overnight once the touch in and touch out information is downloaded from the gates and collated.^[118] When a touch in with a contactless card is made, the validity of the card is checked by debiting the card account with 10 pence. The final fare charged excludes this initial charge. As with Oyster, a failure to touch either in or out, charges the maximum possible fare. Transport for London state that if ticket inspection is taking place, it is then necessary to present the contactless card to the ticket inspector's portable oyster card reader. As the reader at the starting station cannot write to the contactless card and the card's use is not downloaded until the following night, it is not possible to determine if the card was used to touch into the system. However after concilation if it was found that the card was not touched in at the moment of revenue inspection, a maximum fare would be charged as a failed revenue inspection and the card may be blocked from further use.^[119]

App

In late 2017, TfL introduced the free Oyster card app which allows users to check their balance on a compatible Android or iOS smartphone. Users can top up their Oyster card on the go, and check journey history. Top-ups are available to collect at any London Underground station or bus within 30 minutes. The app can notify users when their balance drops below a specified amount.

First-generation Oyster cards, identified by not having a "D" at the bottom left corner of the back (see images of the back of both generation cards above), can be used but are not compatible with the app, and TfL recommends that users get a new card, and transfer credit, season tickets, and refundable deposit from the old one.^[120]

Designs

Trial versions, Transport for London staff versions and the first version of the standard Oyster card for the public were released with the roundels on the front of the cards in red. Standard issues of the Oyster card have been updated since the first public release in order to meet TfL's Design Standards.

There have been three issues of the standard Oyster card, including the original red roundel issue, but all three Oyster cards have retained their original dimensions of 85mm x 55mm, with Oyster card number and reference number located in the top right-hand corner and bottom right hand corner of the back of the card respectively, along with the terms and conditions.

The second issue of the standard Oyster card had 'Transport for London' branding on the back of the card, with the Mayor of London (having replaced the 'LONDON' branding in the blue segment of the card's back). The roundel on the front of the card was changed from the colour red to white, as white was seen to represent Transport for London (whereas a red roundel is more known to represent London Buses).

The most recent issue of the standard Oyster card has TfL branding on its front, removed from the back of the card in the previous issue. The Mayor of London branding has also been moved from the blue segment on the back of the card to underneath the terms and conditions, where it is more prominent.

Oyster card holder/wallet

With the release of the Oyster card, TfL released an accompanying Oyster card holder to replace the existing designs, previously sponsored by companies such as Yellow Pages, Direct Line and IKEA, as well as London Underground's and London Buses own releases of the holder which came without advertising.

The official Oyster branded holders have been redesigned on several occasions, keeping up with various iterations of the card and to increase service awareness. The initial version mimicked the blue design of the card itself, and was later modified to include the line "Please reuse your card" on the front.

In March 2007 the Oyster card wallet was designed by British designers including Katharine Hamnett, Frostfrench and Gharani Strok for Oxfam's I'm In campaign to end world poverty. The designer wallets were available for a limited period of time from Oxfam's street teams in London who handed them out to people who signed up to the I'm In movement. Also, to celebrate 100 years of the Piccadilly line, a series of limited edition Oyster card wallets were commissioned from selected artists from the Thin Cities Platform for Art project. The previous wallets handed out were sponsored by IKEA who also sponsor the tube map, and did not display the Oyster or the London Underground logos.

In late 2007 the standard issue wallets were redesigned with the only changes being the colour scheme changing from blue to black, and the removal of the resemblance to the Oyster card.

The most recent variation of the wallet came with the introduction of contactless payment acceptance on the network in 2012, where light-green "Watch out for card clash" wallets have been issued to raise awareness of "card clash", and replace the previous simplistic designs. The inside of these wallets reads "Only touch one card on the reader" on the clear plastic.

In 2015 Mel Elliot won the London Design Awards with her "Girls Night Out" themed wallet.^[121]

In addition to the official wallets distributed by TfL, which may or may not carry advertising for a sponsor, Oyster card holders and wallets are sometimes used as a marketing tool by other organisations seeking to promote their identity or activities. Such items are normally given away free, either with products or handed out to the public.

Historically, customers were given a free wallet when purchasing a card, and wallets could be picked up for free at most stations or newsagents, though in September 2019 TfL announced that they were discontinuing their free Oyster Card wallets citing the cost and also the use of plastic.

Staff cards

The standard public Oyster card is blue but colour variants are used by transport staff. Similar cards are issued to police officers.

Variants

The standard Oyster card designs are as follows:

• Standard Oyster card, Blue: Design has remained mostly the same since its introduction in 2003, but very minor text changes on the reverse continue to occur. These are issued when limited edition cards are not in circulation
• One Day Bus and Tram Pass, Green: Introduced in January 2015, this card carries the "Oyster" branding and can only be used for a maximum of one day, as it can not be reloaded with credit. It is half the thickness of a standard Oyster card, as it is meant to be discarded when it expires. The card allows the user unlimited travel on bus and tram until the next day.
• Visitor Oyster Card: A visitor card is designed for use by tourists to London and can be delivered to their home address before they arrive. Tourists can benefit from special offers and discounts and save money in leading London restaurants, shops and entertainment venues on presentation of this card. A discount is also offered on the London Cable Car service.

A number of limited edition Oyster card variant designs exist. These are produced in limited quantities but otherwise function as standard Oyster cards. These include:

• 2011 Wedding of Prince William and Catherine Middleton. (750k produced) ^[122]
• 2012 Queen Elizabeth II's Diamond Jubilee Portrait Version. (250k issued) ^[122]
• 2012 Queen Elizabeth II's Diamond Jubilee Buckingham Palace Edition. (1.5m issued) ^[122]
• 2012 London 2012 Games - various designs listed below.
• 2012 150th Anniversary of London Underground. (1m produced) ^[122]
• 2014 TfL Year of the Bus. (1.4m produced) ^[122]
• 2018 Adidas x TfL (3 variations with 500 of each produced).^[122]
• 2022 Adidas Arsenal (1000 produced)^[122]
• 2022 Elizabeth Line^[123]
• 2023 Oyster 20th anniversary^[124]

In 2012, TfL released various cards to mark the Olympic Games taking place in London that year. The cards performed the same as any other card and also include all the same text, apart from a differentiating line (listed below), and the London 2012 logo. Cards like these were distributed solely to select 2012 volunteers who took part in the opening and closing ceremonies. They were used for the duration of the games and therefore are no longer valid for use on the transport system. The colour of these Oyster cards is pink with a coloured stripe:

• "London Olympic Games", Pink stripe.
• "London Paralympic Games", Blue stripe.
• "Olympic Volunteer", Green stripe.
• "Paralympic Volunteer", Orange Stripe.
• "2012 Ceremonies Volunteer", Purple stripe.

Three design variations of the Oyster visitor cards also exist:

• 2007 Tutankhamun and the Golden Age of the Pharaohs exhibition at the O2.
• 2007 Standard version showing the London Eye, St Paul's Cathedral, 30 St Mary Axe and the Millennium Bridge.
• 2012 Visitor Oyster card containing letters made up of landmarks spelling LONDON.

Touching out penalties

Card users sometimes forget to touch in or touch out, are unable to find the yellow readers or it may be too crowded to touch out. Such card users have either received penalty fares by revenue inspectors, been charged a maximum fare, or been prosecuted in courts which can issue high penalties.^[126] Card users are also penalised for touching in and out of the same station within a two-minute period, and charged the maximum possible fare from that station.^[127]

The system also applies two maximum fares (one for touching in, and one for touching out) to passengers who touch in and touch out at the same station after 30 minutes; this is due to the system assuming that, after such a long delay, the passenger has travelled to another station and returned without touching in or out at the other station, when in reality the passenger might simply have been waiting for a train, baulked at the long waiting time and exited.

Extension fares

Holders of Travelcards can add pay-as-you-go credit on their Oyster cards. This credit is used as 'extension fare' when users travel beyond the zones in which their Travelcard is valid. This extension fare equals the regular Oyster fare for a journey from/to the respective station outside of the validity area of the Travelcard to/from the closest zone still covered by the Travelcard. To distinguish between peak and off-peak fares, however, the start of the journey is taken into account. That means travellers might be charged the (more expensive) peak fare as extension fare even if they had not yet left the area of validity of their Travelcard by the end of peak time. Conversely, a journey starting in the covered zones shortly before the start of the peak time will be charged as off-peak.

There is an exploitable feature of the system, in that if a touch-in (or touch-out) is made in a zone where the oyster card is loaded with a valid season ticket or Travelcard but there is no associated touch-out (or touch-in), the system does not change a fare. Although encouraged to do so, such ticket holders are not obliged to touch-in or touch-out within the zones of their ticket's validity (other than to operate a barrier), and may in fact be impossible to do so when combining with a paper extension ticket for travelling outside the zones. This means that a passenger holding (say) a valid zone 1&2 Travelcard, can touch-in at a zone 1 station (to open the ticket barrier) and then travel to a zone 3, 4, 5 or 6 station that does not have a barrier without touching out or paying the extension fare. Ticket inspectors frequently operate at such locations to catch these fare dodging passengers. Since the system maintains a record of every touch the card does make (even with a valid travelcard), TfL will assiduously seek to recover all the unpaid fares when a passenger who is caught is prosecuted for fare evasion.

From January 2010 to May 2011, passengers using an Oyster card with a Travelcard loaded seeking to start a journey in their paid-for zones and end it outside those zones were expected to use a ticket vending machine to set an Oyster Extension Permit (OEP) on their card before starting their journey. The effect of this setting was that a maximum journey charge was deducted from the card when touching in even within their zones, and this removed the incentive to "forget" to touch-out at the end of the journey. The OEP system was poorly-understood by staff and passengers alike and was abolished after less than a year and a half.^[128][129]

Privacy

The system has been criticised as a threat to the privacy of its users. Each Oyster card is uniquely numbered, and registration is required for monthly or longer tickets, which are no longer available on paper. Limited usage data is stored on the card. Journey and transaction history is held centrally by Transport for London for up to eight weeks, after which the transactions and journey history are disassociated from the Oyster card and cannot be re-associated; full registration details are held centrally and not on individual Oyster cards; recent usage can be checked by anyone in possession of the card at some ticket machines.^[130]

The police have used Oyster card data as an investigative tool, and this use is increasing. On 13 April 2006, TfL stated that "Between August 2004 and March 2006 TfL's Information Access and Compliance Team received 436 requests from the police for Oyster card information. Of these, 409 requests were granted and the data were released to the police."^[131] However, in response to another request in February 2012, "TfL said this had happened 5,295 times in 2008, 5,359 in 2009, 5,046 in 2010, and a record 6,258 in 2011".^[132]

Additionally, in 2008 news reports indicated that the security services were seeking access to all Oyster card data for the purposes of counter-terrorism. Such access is not provided to the security services.^[133]

As yet, there have been no reports of customer data being misused, outside the terms of the registration agreement. There have been no reports of Oyster data being lost.

Design

The system has been criticised for usability issues in general system, website and top-up machine design.^[134]

Oyster pay-as-you-go users, on London Underground, DLR and National Rail (including London Overground) services are required always to "touch in" and "touch out" to cause the correct fare to be charged. This requirement is less obviously enforced at stations where there are only standalone yellow reader rather than ticket barriers. Without a physical barrier, pay-as-you-go users may simply forget to "touch in" or fail to touch their card correctly, which will result in a maximum fare being charged. Equally, if the barriers do not function (reading 'SEEK ASSISTANCE') and the TfL or train operating company staff member has to open the gates manually, then the maximum fare may be charged. If this occurs a refund may be requested by telephoning the Oyster helpline the day after the incident occurs (to allow time for the central computers to be updated); the overcharged amount can be added back to the pay-as-you-go balance on the card from the following day when the Oyster card is used to make a journey.

The use of Oyster cards on buses has been subject to criticism following a number of successful criminal prosecutions by TfL of bus passengers whose Oyster card, when checked by Revenue Protection Inspectors, did not show that the passenger had "touched in" correctly on boarding.^{[135][136][137]} In particular, problems have been highlighted in connection with the quality of error messages given to passengers when touching in has failed for any reason. In one case, a passenger successfully appealed against his conviction for fare evasion when the court noted that the passenger believed he had paid for his journey because the Oyster reader did not give sufficient error warning.^[138][139]

In 2011, London Assembly member Caroline Pidgeon obtained figures from the Mayor of London which revealed that in 2010, £60million had been taken by TfL in maximum Oyster fares. The statistics also detailed a "top ten" of stations where maximum fares were being collected, notably Waterloo and London Bridge. In her criticism of the figures, Pidgeon claimed that "structural problems" with the Oyster system were to blame, such as faulty equipment failing to register cards and difficulty in obtaining refunds.^[140][141] A report by BBC London highlighted the system of "autocomplete" (in which Oyster cards journeys are automatically completed without the need to physically touch out, exceptionally used when large crowds are exiting stations) as particularly problematic.^[142]

Technical faults

In January 2004, on the day that the pay-as-you-go system went live on all Oyster cards, some season ticket passengers were prevented from making a second journey on their travelcard. Upon investigation each had a negative prepay balance. This was widely reported as a major bug in the system.^[143] However, the reason for the "bug" was that some season ticket holders were passing through zones not included on their tickets, and the holders had been correctly charged pay-as-you-go fares for the zones they hadn't paid for. The existing paper system, and the previous Travelcard-only system, could not prevent this kind of misuse as the barriers only checked if a paper ticket was valid in the zone the barrier was in.

On 10 March 2005 an incorrect data table meant that the Oyster system was inoperable during the morning rush hour. Ticket barriers had to be left open and pay as you go fares could not be collected.^[144]

On 12 July 2008 an incorrect data table disabled an estimated 72,000 Oyster cards, including Travelcards, staff passes, Freedom Passes, child Oyster cards and other electronic tickets. The Oyster system was shut down and later restarted during traffic hours. Some customers already in the system were overcharged. Refunds were given to those affected and all disabled cards were replaced. Freedom Pass holders had to apply to their local authority for replacement passes (as these are not managed by TfL).^[145]

A further system failure occurred two weeks later on 25 July 2008, when pay as you go cards were not read properly.^[146]

On 2 January 2016 the Oyster system failed, with readers failing to process Oyster cards but continuing to process contactless cards and Apple Pay transactions.^[147]

The difference between pay as you go and Travelcards

Transport for London promoted the Oyster card at launch with many adverts seeking to portray it as an alternative to the paper Travelcard. In late 2005 the Advertising Standards Authority ordered the withdrawal of one such poster which claimed that Oyster pay as you go was "more convenient" than Travelcards with "no need to plan in advance". The ASA ruled that the two products were not directly comparable, mainly because the pay as you go facility was not valid on most National Rail routes at the time.^[148][149]

Transport for London has made a significant surplus from excess fares deducted for those travelling using PAYG and failing to touch out as they exit stations. According to information obtained under the Freedom of Information Act^[150] TfL made £32m from pay as you go cards of which £18m was maximum fares for failing to touch out. Only £803,000 was paid in refunds, showing that whilst customers can apply for a refund, most do not. The oyster online site does not list all maximum fares eligible for refunds on the front page, and users must search for fares charged on a particular day to discover all maximum fares that have been charged. The maximum fares for failing to touch out were introduced late 2006.^[151]

Validity on National Rail

Until the availability of Oyster pay-as-you-go on the whole of the National Rail suburban network in January 2010, the validity of PAYG was not consistent across different modes of transport within London, and this gave rise to confusion for Oyster pay-as-you-go users.^[152] Many passengers were caught out trying to use Pay as you go on rail routes where it was not valid.^[153][154]

On some National Rail routes where pay-as-you-go was valid, Oyster validators had not been installed at some intermediate stations. While Oyster pay-as-you-go users could legally travel along those lines to certain destinations, they were not permitted to board or alight at intermediate stations. If their journey began or ended at an intermediate station, they would be unable to touch out and consequently be liable for penalty fares or prosecution.^[155][156]

The complexity of Oyster validity on these routes was criticised for increasing the risk of passengers inadvertently failing to pay the correct fare. Criticism was also levelled at train operating companies for failing to provide adequate warnings to passengers about Oyster validity on their routes and for not installing Oyster readers at certain stations.^[157][158]

TfL published guides to the limitations of pay-as-you-go validity^[159] diagrammatic maps illustrating PAYG validity were published in November 2006 by National Rail,^[160] but these were rarely on display at stations and had to be obtained from transport websites.^[157]

Online and telesales

Historically, Oyster card ticket renewals and pay-as-you-go top-ups made online allow users to make purchases without the need to go to a ticket office or vending machine. However, there were certain limitations to this system:

• tickets and pay-as-you-go funds can only be added to the Oyster card from 30 minutes after purchase (if bought online);
• users must select a station or tram stop where they must touch in or out as part of a normal journey to complete the purchase (as cards cannot be credited remotely);
• users must nominate the station in advance – failure to enter or exit via this station means that the ticket is not added to the card;
• tickets purchased in this way could not be added from a bus reader (due to these not being fixed in a permanent location).^[161]

Now only the 30 minutes limitation, and the requirement to make a journey still exist. Users no longer need to select a station and can collect the ticket or top up made online at any stations, including on a bus, while making the next journey.

Security issues

In June 2008, researchers at the Radboud University in Nijmegen, the Netherlands, who had previously succeeded in hacking the OV-chipkaart (the Dutch public transport chip card), hacked an Oyster card, which is also based on the MIFARE Classic chip. They scanned a card reader to obtain its cryptographic key, then used a wireless antenna attached to a laptop computer to brush up against passengers on the London Underground and extract the information from their cards. With that information they were able to clone a card, add credit to it, and use it to travel on the Underground for at least a day.^[162][163] The MIFARE chip manufacturers NXP Semiconductor sought a court injunction to prevent the publication of the details of this security breach, but this was overturned on appeal.^[164]

The Mifare Classic—which is also used as a security pass for controlling entry into buildings—has been criticised as having very poor security, and NXP criticised for trying to ensure security by obscurity rather than strong encryption.^[165] Breaching security on Oyster cards should not allow unauthorised use for more than a day, as TfL promises to turn off any cloned cards within 24 hours, but a cloned Mifare Classic can allow entry into buildings that use this system for security.