Michael Brent Knowler, 59, pleaded guilty at the online Ballarat Magistrates' Court on Thursday to two counts of dangerous driving causing death and one count of dangerous driving causing serious injury.

Knowler was driving a Kenworth prime mover on Church Parade towards his friend's home in Broomfield on December 29 when he failed to give way at the intersection and collided with a Toyota Rav4 causing it to flip.

Jess West, 37, and her five-year-old son Deighton died at the scene. The driver, Anthony West and another passenger, nine-year-old Oakley, received injuries.

Knowler, who was using a GPS on his phone to assist with directions to Broomfield, told police he checked his mobile phone before the intersection and it told him to continue straight.

He said he had seen the yellow and black sign indicating the upcoming intersection 240 metres before and had seen the white line on the road at the intersection indicating he must give way, but he did not see the give way sign.

Knowler told police he was not 'consciously looking' for it, as he had seen the white line. He had slowed down at the intersection, looked left and saw no traffic, but he could not see to the right as trees obscured his view.

Knowler had only seen the Rav4 when he entered the intersection.

The force of the collision tore the bull bar from the prime mover and it stopped about 60 metres west of the intersection after Knowler gained control of the vehicle.

Mrs West was seated in the passenger seat and her five-year-old son Deighton was in the rear passenger side seat. Both died at the scene.

Mr West was transported to hospital with minor injuries, while Oakley was airlifted to the Royal Children's Hospital with facial injuries.

A dog in the car died at the scene.

The prosecution withdrew two alternative charges on Thursday on the basis Knowler would plead guilty to the three remaining charges.

The matter was set down for a committal hearing but the court was informed it had resolved.

When asked if he was pleading guilty or not guilty, Knowler replied, "I plead guilty Your Honour to three charges". The victims' husband and father, Anthony West, was at the hearing.

Knowler was placed on trial bail to appear at the County Court on February 22 for a plea hearing.

His bail conditions include to live at Broomfield, not to contact prosecution witnesses other than the informant and report to the Ballarat Police Station.

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