Passengers gave Auckland's new electric trains high marks for comfort on their first work-day today - before door-opening problems and staff nerves cascaded into delays of up to 25 minutes.

Although beaming faces among commuters made for a novel start to the week, there were grumbles among some who wanted only to get to work on time.

Auckland Mayor Len Brown was effusive at Onehunga Station while waiting for a return trip to Britomart, promising a breakfast television audience a cracking pace once a $520 million fleet of 57 electric trains banishes "the old dinosaur diesels" from Papakura to Swanson by mid to late next year.

"At that point, we'll be running every eight to 10 minutes and that's what people want - they don't want to be mucking around waiting."


But moments later, a sigh of dismay rippled around a crowd of about 80 waiting passengers at an announced 12-minute delay to their 7.10am service.

The history-making first train out of Onehunga had left just two minutes late at 5.48am, its silence and smooth motion almost imperceptible to some passengers, as the platform slipped behind them in the darkness.

By 9.30am, however services were running 25 minutes late.

That forced rail operator Transdev to cancel a return trip on the Onehunga-Britomart run and and bring in a third train to get back on schedule by about midday.

Its troubles were compounded yesterday evening by disruptions to diesel trains on the western line after a pedestrian was knocked down and seriously injured on tracks near Henderson.

But at least it did not have to call on a small fleet of replacement buses it had on standby at Onehunga in case of any mechanical meltdowns.

Auckland Transport apologised for "minor delays as train changes bed in", putting those down to rail staff being extra vigilant while supervising boarding passengers who were unfamiliar with new green buttons used to open and shut the wide doors on the three-car electrics.

"It is not a fault with the trains, it's a mixture of staff being cautious and customers being eager to embrace the new technology," said chief operations officer Greg Edmonds.

A Transdev spokeswoman said the company had adjusted procedures at Britomart "for the time being so that all doors are opened on arrival and stay open until departure, and we'll review [that] as the trains settle in and people get used to them."

And as his late service picked up pace on an incline between Ellerslie and Greenlane at about twice that of old diesels struggling to get much faster than 40km/h, Mr Brown quipped: "It's like we're going downhill - we should have a speedometer outside to show off to motorists."