A man who killed a mother and daughter when his car slammed into theirs as they left a parent-teacher night in Melbourne's outer south-east, has been sentenced to 13 years in prison.

Key points: Thomas Adamson was disqualified from driving at the time of the fatal crash

Thomas Adamson was disqualified from driving at the time of the fatal crash Witnesses reported he was driving so fast his car sounded like a jet

Witnesses reported he was driving so fast his car sounded like a jet The husband and father of the victims told the court he felt "helpless"

Thomas Charles Adamson, 27, was travelling at 155 kilometres per hour and had a blood alcohol content of between 0.125 and 0.165 per cent when he smashed into the car carrying Ma Li Dai, 44, and Xinyu Yuan, 14, in August 2017.

The pair had just left the Lighthouse Christian College in Cranbourne East, and were travelling at just 16kph when they pulled out on to the South Gippsland Highway.

In sentencing Adamson in the County Court, Judge Trevor Wraight told him his actions were "self-indulgent" and he had shown "no regard for others".

"Two innocent lives were lost because of your driving," Judge Wraight said.

Adamson had already had been disqualified from driving for speeding and drink driving offences at the time of the crash.

Witnesses said Adamson was driving so fast his car sounded like a jet. ( ABC News )

Judge Wraight said witnesses had described Adamson's car as "sounding like a jet" and "flying" down the highway.

Members of both the victims' family and Adamson's family shed tears as Judge Wraight sentenced him to nine years' jail for each charge of culpable driving causing death.

Four years of the sentence will be served consecutively for an effective sentence of 13 years.

He will have to serve nine years before being eligible for parole.

Judge Wraight said that if Adamson had not pleaded guilty, and saved witnesses the pain of a trial, he would have been sentenced to 16 years.

In a victim impact statement read in part by the judge during sentencing, Ma Li Dai's husband said: "I feel helpless, I am so sad, and I am crying, my eyes are crying, my tears are running out".

Neither family spoke outside court.