Auckland Transport says a crack-down on passengers dodging train fares already appears to be having an effect.
It believes 6-8% passengers are riding trains without buying tickets, meaning a loss of about $5 million in sales.
Officials have been carrying out random inspections at stations, checking every passenger getting on and off trains.
From Monday inspections were being carried out across the network with officials putting up blockades at stations and checking travel cards and tickets.
Auckland Transport operations manager Greg Edmonds said there had been a couple of calls from commuters backing the operation, which will continue for the next few weeks.
The early indication from the trial scheme shows the number of fare evaders may drop below 5%.
From 7 April the penalty for travelling without a ticket rose to $20 and moves are being made to change laws to allow hefty instant fines.