That is believed to be under consideration for crime-fighting protocols being negotiated by Auckland Transport, train operator Transdev, police and others.
Although spray cans and rocks cause the most visible damage, hurled eggs also create problems once dry.
Tags etched into seat backs and windows are another bugbear. Protective film can be peeled off the double-glazed windows and replaced for about $100 a time.
But seat backs have to be sent away for repair, prompting Auckland Transport to consider attaching film to them as well.
An audit last month found 15 per cent of seat backs throughout the electric fleet had been scratched or gouged with sharp objects, and half the windows in one carriage the Herald was invited to inspect were etched into.
Electric trains integration manager Allan Gordon said an escalation in damage since the new fleet started running full-time on the southern rail line to Papakura was running down seat back stocks.
Although a gallery of suspects is being compiled, a big challenge is to put names to faces. That should become easier once new legislation is introduced next year to require fare evaders to provide names and addresses to council-appointed enforcement officers, or face fines of up to $1000.
Auckland Transport chairman Lester Levy says fare evasion often goes hand-in-hand with other anti-social behaviour.
