The three sisters, aged 12, 13 and 19, were forced off a train by inspectors when they were found to be travelling without tickets.
Three uncles of the girls have instructed a lawyer to issue a complaint to national train operator SNCF for its failure to act in accordance with guidelines over the treatment of young people travelling without tickets.
"This complaint is directed at the SNCF inspector and the company who ought to have informed police given the involvement of minors," said the family's lawyer on Monday, reported radio station Europe 1.
Around midnight on Friday, Carmen, aged 12, Charlotte, 13 and Victorine, 19, were walking along the A7 autoroute which runs between the southern cities of Lyon and Marseille.
An employee of the company running the motorway reported that he saw the girls while patrolling the stretch of motorway.
He spoke to the girls and asked them to walk behind the barriers but they refused.
They were later hit by cars as they ran across the motorway.
The three girls lived in Marseille and were part of the city's traveller community.