You said there should be ticket barriers at ALL stations in your previous post, so the entire network would be similar to London Underground. That would mean the passenger has to pass through a ticket barrier at both their entry and exit station, which ever stations they use, so for instance someone with a London Bridge platform ticket only would not be able to exit Greenwich station without first purchasing a new ticket. So if you're now arguing that on board ticket checks at also required is the same required on London Underground?
London Underground have a very active revenue protection unit, supported by the BT Police.
My point was, I thought, quite simple.
A ticket is needed to pass through the entry and exit barriers. Someone travelling on a platform ticket would thus not get anywhere, because the system would not let them exit.
That leaves the evaders who operate on "short journey" evasion, as in the Southend V to Liverpool St scenario. In this case they buy a Southend V to Rochford and a Straford to Liverpool St. They have tickets which would let them enter and more importantly exit, yet the have not paid the intermediate fare.
A system use in many South American cities and elsewhere in the World is one where there is a flat fare throughout the whole system. A ticket is bought from the booking office and is then taken by the barrier as you enter the system. You thus pay each time you enter the system. Such systems make large sums of money such that every station is manned by both station and security staff, fare evasion though is no-existent because you have to pay to get into the system.
Once inside you can travel anywhere you want, to use a UK example, Croydon to St Albans would be the same price as London Bridge to Blackfriars. These systems however are different from ours in that they actually make money and incredibly busy.
It would take an enormous change of approach in the UK and would require an incredible amount of Political courage - the sort that this Political system would never reward but would only destroy the person proposing it through the medium of others using it for cynical Political positioning purposes, similar to what happened after Clapham, Southall, Ladbroke Grove, Hatfield, Potters Bar.
