Delays signalled as new services are bedded in on lines from Papakura and Swanson.

Auckland Transport is warning passengers of potential bedding-in glitches after it replaces diesel trains this morning with electrics on all lines from Papakura and Swanson to Britomart.

The council body says running times this month have improved on poor punctuality and reliability suffered by passengers in May and June, and expects more progress once it is no longer lumbered by maintenance problems with its elderly diesel fleet and crew shortages exacerbated by training demands.

Mayor Len Brown is hailing today's completion of the electrification roll-out as "a revolutionary era for public transport" and "an example of us working with Government on major transport issues".

But Auckland Transport rail services manager Craig Inger says it is inevitable there will be "issues" during a bedding-in period over coming months.

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"We hope we can keep any disruption to a minimum but overseas experience shows we have to be prepared for the possibility."

The electric trains have been introduced in stages since April last year. But although they are quieter and more comfortable than the diesels, problems have included over-sensitive electronic speed controls and longer "dwell" times at stations caused by the extra time it takes for passengers to open and shut their doors.

That has cancelled savings from faster acceleration and braking, adding up to four minutes in scheduled running times on the western line, the final section of Auckland's network to be electrified.

A work programme developed by Auckland Transport and KiwiRail for the next 12 months includes provision for faster approaches to signals and stations, and consideration of automatic door controls.

Timetables have been adjusted to allow daily diesel shuttles between Pukekohe and Papakura from today and buses will replace trains between Waitakere and Swanson.

Electrification costs
•Power supply, signalling and civil works - $500 million (government-funded)
•57 three-car electric trains - $540 million (joint government-Auckland Council funding)
•Wiri maintenance depot - $100 million (joint funding)