You can save on London train costs by using an electronic Oyster pay-as-you-go (PAYG) card rather than paying by cash or card.
Before the weekend, PAYG was largely only valid on tubes, buses, trams and river services.
But Transport for London (TfL) extended the scheme to cover all overground services within its nine travel zones from 2 January. It will also be accepted in a few c2c stations in Essex (see the Cheap Train Tickets guide).
A TfL spokeswoman says that "overall, Oyster offers the cheapest single rail fares applicable on most overground services".
- A journey from Surbiton (Zone 6, in Surrey) to Waterloo (Zone 1) costs £5 if you buy a ticket on the day at any time or £4.90 if using PAYG during peak hours and £3.20 off peak.
- Surbiton to Oxford Circus (Zone 1) costs £7 with a paper ticket, £6 (PAYG peak), or £4.30 (PAYG off peak).
PAYG also caps prices per day at the equivalent one-day travelcard cost.
The only type of Oyster card previously valid on most train services were seven-day or longer season tickets.
The changes will mainly help occasional travellers without a season ticket.
Those who tried to use PAYG on overground services in the past, assuming they were allowed to, will also be spared the £50 fare evasion fine (plus possible prosecution).
While PAYG is cheaper than buying a paper ticket, many fares across the capital have risen this week.
TfL says average bus fares are up 12.7% and Tube fares are up typically up 3.9%.
For example, an Oyster PAYG bus fare has risen from £1 to £1.20, while a tube journey on Oyster PAYG within zone 1 has risen from £1.60 to £1.80.
The majority of travelcard prices have been frozen.
Mayor of London Boris Johnson says: "I know fares rises will be hard, but believe me, without them, the huge improvements in our quality of life, and the retention of the standing of our city, would not be possible."
On the trains nationwide, including London, most season tickets have fallen in price by 0.4%, apart from on South Eastern and West Yorkshire 'Metro' fares, which have risen.
Off-peak and advanced fare prices have risen by an average 1.1%.
Further reading/Key links
Cut travel costs: Cheap Train Tickets, Cheap UK Travel