The Oyster system charges a price for each journey made. In the case of National Rail, Underground, Overground and DLR each journey is allowed to include more than one mode as long as the gap between sections is reasonable. Sometimes you can change between modes without touching out and in (eg between National Rail and DLR at Greenwich), but usually it is necessary. The system is programmed with a number of such interchanges. The time allowed varies dependant on the distance involved and the frequency of trains on the next leg. Thus an Underground to National Rail OSI will often allow more time than the opposite National Rail to Underground OSI, particularly if passengers usually wait on a concourse until their train is advertised.
Unfortunately this is one of the hidden caveats that TfL seem reluctant to publish. The reason given is that the list and timings are under constant review as circumstances change. The table has been removed as it is now out of date.
The Oyster Control Centre has the ability to set and remove emergency OSIs in real time according to locally made requests. These will typically cater for short term (un)planned station closures and some weekend engineering work. An EOSI will be set at a number of stations and will allow interchange between any of those stations within 30 minutes, including re-entering the same station. These EOSIs are not included in the table because of their extremely fluid nature.
Change introduced in May 2013 List
- OSI between Kings Cross St Pancras and St Pancras Intl NR increased to 30 minutes.
Changes introduced in October 2012 List
- New OSI between Ickenham and West Ruislip.
- New OSIs between gatelines at Richmond and Woodford.
- Deleted OSI between seperate parts of Wembley Central.
- OSI between Kings Cross St Pancras and Kings Cross NR increased to 40 minutes.
Changes introduced in January 2012 List
- New OSI between Aldgate LU and Tower Gateway DLR.
- New OSI between Edgware Road LU stations.
- New OSIs between gatelines at Farringdon and Oxford Circus.
Changes introduced in May 2011 List
- New OSI between Cannon Street NR and Bank LU.
- New OSI between Finsbury Park LU and NR.
- New OSI between Putney NR and East Putney LU.
Temporary OSI between Goodge Street, Leicester Square and Tottenham Court Road.
Change introduced in November 2010 List
- New OSI between Cannon Street NR and Mansion House LU.
Changes introduced in September 2010 List
- Addition of a new entrance to Canary Wharf Tube called E2.
- New OSI between different gatelines at Paddington LU.
Changes introduced in October 2010 ATOC List
These changes have been ignored because they were not borne out in the TfL list.
New OSIs between Bank and Cannon Street, Mansion House. OSI between Kings Cross/St Pancras and Kings Cross NR increased to 40 minutes. OSI between Mansion House/Temple and Blackfriars NR reduced to 20 minutes. OSIs between Paddington gatelines and P8/9 PVALs reduced to 20 minutes. OSI between Southwark and Waterloo East increased to 40 minutes. OSI between St Pancras NR and Kings Cross NR increased to 40 minutes. OSI between Waterloo East and Southwark increased to 20 minutes.