Three women breastfeeding their babies in cars on Auckland's motorways were fined $150.



Auckland motorways manager Inspector Shanan Gray said police were "shocked" at the discovery, saying it put everyone in an "extremely dangerous situation".



"If they had to stop their vehicle suddenly, or they were involved in a serious crash, the infant would surely be ejected from the vehicle," he said.



"There's no question it's going to cause serious injury if not death to the child."



The experienced officer said he had never come across the issue before the 10-day child restraint blitz, which ended last Thursday.



"It demonstrates that there are people out there who don't have a true understanding or appreciation of the forces involved in a crash or a sudden stop in a motor vehicle.



"If you think you can hold on to your child during an incident like that and keep them in the vehicle, then unfortunately physics won't allow it."



The cars were stopped and the mothers "spoken to", given instructions on how to properly restrain a child and issued with a $150 fine, he said.



Gray said police were "further stunned" by the number of small children discovered in foot wells and car boots.



Police found a newborn baby in a capsule on the front seat of a vehicle that was fitted with an airbag - in spite of extensive warnings in the vehicle that this was not safe.



Gray said there was a mixture of people who set off with unrestrained children "or on the other hand there's parents who if they're travelling feel its time for a feed and they'll take the child out of the restraint and feed them in the vehicle as they travel along".



"We need to get the message across that that's a very, very dangerous situation for that child to be in, in the result of a crash or a sudden stop. The outcome's inevitable."



Gray said the operation was the result of a recent increase in the number of serious crashes where children had been the passengers.



"Crash data shows that in the majority of these cases the children were either inappropriately restrained or not restrained at all," he said.



Gray said that over the 10 days, most drivers spoken to about child restraints displayed some knowledge and meant well but failed to understand the minimum safety requirements.



The number of young children who were found to be at risk by having an incorrectly fitted restraint or no restraint at all was "hugely disappointing".



"The safest place for a child is in the back seat, until the child is at least 10 years old as their bodies have not fully developed, so they are more susceptible to traumatic injury.



"It's essential that adults always wear their seatbelts as they are the role models to their children," he said.



Information on how to legally restrain children in vehicles can be found on the NZTA website.

* Clarification: This story originally reported the breastfeeding mothers were driving, based on incorrect information in a police press release. They were in fact passengers in the cars.