Defence lawyer Peter Brosnahan said the facts of the case were "somewhat unusual".
Mr Brosnahan hired a traffic investigator to look at how Griggs, who pulled on to State Highway 2 at Pakipaki from State Highway 50A, failed to see the other car on the afternoon of July 31, 2014.
An in-cab camera showed how the accident played out, he said.
"You can see as he approaches the intersection he carefully checks the right. Then in his mind the way is clear and he then concentrates on the left.
"At the time Mr Griggs has looked to the right, the vehicle has been obstructed by a large give-way sign.
"While the car was there to be seen and he missed it, that's the explanation for it."
The investigator had taken measurements and assessed footage to show how the car could be missed.
Mr Brosnahan said signs around the intersection, which the victim's father described as a black spot, had since been changed.
"The victim's father says in some ways this accident has been a blessing in disguise because finally we've got the NZTA doing something about this intersection."
While the sign might have obstructed his view, Griggs should have been aware of it and been more cautious, Mr Brosnahan said.
"It's not put forward by Mr Griggs as an excuse, it is there as the reason. It certainly is low-end, low-level carelessness."
Griggs and the victims' families had now become "firm friends", he said.
They attended a Restorative Justice conference, which went positively. Griggs was now Facebook friends with the driver of the other car.
Judge Cameron said the victim had to have surgery for "severe abdominal injuries" and had a broken nose after the crash. Her elder daughter received a cut above her eye and a chipped bone in her arm.
Griggs has previous driving convictions ranging from 1977 to 1997, the judge said.
Mr Brosnahan suggested Judge Cameron should not fine Griggs and instead make a higher order for emotional harm reparation.
Judge Cameron agreed, sentencing Griggs to the minimum driving disqualification period of six months. He also ordered Griggs to pay $2500 reparation for the victims. NZME