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Most Auckland rail commuters will face timetable changes this morning, to allow extra services through an expanded network from Pukekohe to Helensville.

That has brought a warning from rail safety officials for drivers and pedestrians to be extra careful at level crossings, especially if these are on their regular travel routes where they may not expect to meet trains at certain times of the day.

New timetables introduced yesterday include a doubling of peak-period trains running between Swanson and Henderson to four an hour in each direction and extra services between Pukekohe and Britomart.

The first scheduled passenger train to run between Helensville and Auckland since 1980 is due to begin a year-long trial at 6.32am today for a 95-minute trip to Britomart.

That will mark a 27 per cent expansion of the region's passenger network to 140km, after improvements by Ontrack to about half of the 30km section of railway line between Waitakere Station and Helensville, to minimise speed restrictions.

The Auckland Regional Transport Authority has also spent about $900,000 building new platforms at Helensville, Waimauku and Huapai to allow passengers to join the train before it calls at all other stations from Waitakere to New Lynn.

Although the daily trip back from Britomart to Helensville will not be until 5.30pm, and there will be no weekend trains, Norwest Rail Action Group chairman Scott Osmond is confident community support will make the trial successful and see more services added.

He said yesterday he was pleased the transport authority agreed to a request by his group to allow passengers to travel on the evening train's return run to Auckland, leaving Helensville at 7.15pm.

Although about 15 freight trains pass through Helensville each week, the resurrection of passenger services has prompted warnings from the authority and Ontrack for drivers and pedestrians to be extra- cautious at level crossings.

Authority customer services general manager Mark Lambert said care should be taken throughout the region, in view of extra services from Pukekohe and an 18 per cent increase in seating capacity on western line trains.

Ontrack northern manager Steve Collett said people who crossed railway lines at set times should always check that the way was clear.