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Auckland rail passengers are in for another boost next month, when a gap in weekday off-peak services between Papakura and Britomart will narrow to a train departure about every 15 minutes.

That will represent a doubling of services on the southern and eastern lines between 10am and 2pm, bringing them close to peak-time frequencies.

The new timetable will start operating on December 4, when the Auckland Regional Transport Authority and rail operator Veolia will also introduce an extra service for each of the morning and evening peak periods between Otahuhu and Britomart via Newmarket.

Because about half the rail services between Papakura and Britomart use the eastern line, via Glen Innes and the waterfront, Newmarket has until now had to make do with just one train an hour in each direction in day-time off-peak periods. That will rise to one every 30 minutes, a move the rail agencies hope may encourage business people as well as shoppers and students to use trains, even to get to and from meetings.

Transport authority acting chief executive Elena Trout said passenger loads had jumped more than 30 per cent since the last time services were increased, by 25 per cent in October last year, and she hoped for continuing growth as Aucklanders were offered yet more public transport options.

"While we've got a long way to go in terms of developing a comprehensive network, in some areas we're certainly beginning to offer a travel experience that competes with the car," she said.

"We want to develop a system that people are proud to use."

Passengers on the southern and eastern lines were already benefiting from station upgrades at Manurewa, Orakei and Meadowbank, and new stations would be added in the first half of next year at Panmure and Sylvia Park.

Ms Trout said western line passengers could expect similar improvements as more tracks were duplicated between Newmarket and Swanson.

Her organisation is, meanwhile, refuting a claim last week by an Australian transport consultant for the Eden Park Trust Board that Britomart station may be hard-pressed to cope with post-match crowds if a stadium is built on the waterfront for the 2011 Rugby World Cup instead of at Auckland's traditional home of the game.

The transport authority says Britomart can cope with 12,000 passengers an hour - instead of 10,000 suggested by consultant Graeme Steverson - and a greater selection of after-match activities in central Auckland will mean a lesser and more staggered demand for trains than if crowds disgorge from Eden Park to an upgraded Kingsland Station.