A train operator says it is cracking down on fare dodgers who deliberately buy a ticket for only a small part of their journey.
South Western Railway (SWR) said there had been widespread misuse of electronic tickets by passengers.
The operator said it had estimated up to 95% of barcode tickets purchased for the four-minute journey between Vauxhall and London Waterloo were being used fraudulently by people who have travelled much further.
It said so-called short-faring or short-ticketing was putting £31m of revenue at risk.
Since June the company’s trial has identified 153 short-faring offences, compared with seven during the same period last year.
The tickets, which can be bought and displayed on a phone, open the barriers at London Waterloo.
They are considerably cheaper than for long-distance journeys on SWR’s network, which includes Devon, Dorset, Hampshire, Berkshire, Wiltshire, and Surrey.
