Recently I had a discussion with TfL regarding Southeastern Bexley metro stations (stations east of Nunhead) having no Avoid Zone 1 Fare to Thameslink / Southern Stations south of Selhurst despite it may sometime be quicker (and less crowded) to go via Peckham Rye than London Bridge. TfL mentioned that their hands are tied as TOCs are the one who set the routing, not TfL.
This also applies to journeys to the west/north London Underground / Overground /TfL Rail stations, for journeys via Clapham Junction and West London Line, notably with OSI interchange at Shepherds Bush for Central Line (and to District Line/ TfL Rail at Ealing Broadway), or Kenton / Northwick Park (for Metropolitan Line to Uxbridge / Amersham). It is comfortable to go via Clapham Junction with larger trains than the tube in Central London.
(The only avoid zone 1 option is via Stratford for these stations including stations with DLR service, which is not that useful for West London journeys)
As there is a 1.20 - 1.80 London Underground "transfer fare" added to via zone 1 NR - TfL journey, sometimes it would generate some more expensive journey for through journey than 2 journey fare broken at OSI station. For example like Blackheath / Charlton [Z3] - North Acton [Z2/3] (via Clapham Junction and Shepherd's Bush), the through adult off-peak fare would be 4.40 pounds while the combination of two fares broken at Shepherd's Bush would be 3.70 pounds (fare difference can even be more if to zone 3-6 stations). But sad that oyster card is not smart enough to charge two separate fares even if it is cheaper than a through-fare.
This also applies to journeys to the west/north London Underground / Overground /TfL Rail stations, for journeys via Clapham Junction and West London Line, notably with OSI interchange at Shepherds Bush for Central Line (and to District Line/ TfL Rail at Ealing Broadway), or Kenton / Northwick Park (for Metropolitan Line to Uxbridge / Amersham). It is comfortable to go via Clapham Junction with larger trains than the tube in Central London.
(The only avoid zone 1 option is via Stratford for these stations including stations with DLR service, which is not that useful for West London journeys)
As there is a 1.20 - 1.80 London Underground "transfer fare" added to via zone 1 NR - TfL journey, sometimes it would generate some more expensive journey for through journey than 2 journey fare broken at OSI station. For example like Blackheath / Charlton [Z3] - North Acton [Z2/3] (via Clapham Junction and Shepherd's Bush), the through adult off-peak fare would be 4.40 pounds while the combination of two fares broken at Shepherd's Bush would be 3.70 pounds (fare difference can even be more if to zone 3-6 stations). But sad that oyster card is not smart enough to charge two separate fares even if it is cheaper than a through-fare.