Alan Stephens, 40, pleaded not guilty to reckless driving causing manslaughter and three charges of reckless driving causing injury when he appeared in the High Court at Auckland.
Stephens left home on January 20 2009 in his car with his three children Shannyne, six, Trae Blayde, four, and Holly, two and his niece Nakita, 12.
The Crown alleges Stephens drove his car around barrier arms at the railway intersection at Paerata, near Pukekohe, directly into the path of the train which slammed into the back of the car, spinning it around and flinging Nakita out the back window of the car and on to the road.
A jury of seven men and five women was sworn in this morning for a trial set down for two weeks.
Crown prosecutor Kevin Glubb said Stephens' silver Mitsubishi Mirage was seen being driven erratically just before it went onto the railway tracks, where the barrier arms were down, alarm bells were ringing and red lights flashing.
"Within seconds the train came through and crashed into the left rear of the vehicle, pushing it to the other side of the track," he said.
"The rear bumper came off the car as it was spun two or three times. A girl was also seen flying out of the car after the force of the impact. There was a lot of crashing and grinding as the train came to a stop."
The train was travelling at 64kmh and comprised one locomotive and 26 wagons, and once under way would take an "awful lot of stopping", Mr Glubb said.
Stephens told police he did not see the train, but Mr Glubb said a train of that size would have been visible on the tracks.
Trae sustained critical injuries and was flown to hospital by rescue helicopter, where he died later of his injuries. Nakita received severe head injuries and would have serious problems for the rest of her life, the Crown said.
Holly suffered subdural bleeding to the brain and Shannon received cuts and bruises, while Stephens was uninjured.
The accused had displayed appalling driving before the "utterly unacceptable but entirely preventable" collision, Mr Glubb said.
He was cutting corners, and a truck driver saw his car straddle double yellow lines while passing his truck, even with traffic coming the other way.
Two cars had to swerve off the road to avoid Stephens, Mr Glubb said.
Tests later carried out on the barrier arm, lights and bells, found all to be working correctly, and Stephens' car was found to have no mechanical faults.
The Crown was expected to call 24 witnesses, including the train driver, other drivers on the road and witnesses at the scene.
The jury was taken out to the scene this afternoon and the first witness will be called tomorrow.
Quentin Duff, representing Stephens, chose not to make an opening statement today.
