An 18-year-old Frankston man was one of four teenagers killed in a shocking two-car crash at Lynbrook early on Sunday morning.

An 18-year-old Karingal man was killed at 4.50am on Saturday when he was struck by a car while crossing Cranbourne-Frankston Road where it intersects Pindara Boulevard in Langwarrin.

Two single-car accidents, in suburban Balwyn and at Colbinabbin in central Victoria, claimed the lives of two more young men.

Frankston traffic management chief Sergeant Terry Bannan said he could not explain the spate of young deaths on the road.

"I can't give you a reason as to why it's happened," he said. "The young kids think that life is a Nintendo game - they make a mistake, they hit the reset button and everything is fine.

"They are not watching what is going on around them; they believe that it can't happen to them."

The 18-year-old Frankston man was killed when the white Holden Statesman in which he was travelling was involved in a collision with a black Holden Commodore about 1.30am at the intersection of Ormond and Hallam roads in Lynbrook.

The driver of the Commodore, a 19-year-old Narre Warren South man, died on the way to The Alfred hospital.

Two other passengers in the Commodore, a 15-year-old Hampton Park girl and a Narre Warren South girl in her mid-teens, died at the scene.

Two people travelling in the Statesman are fighting for their lives - a 19-year-old Seaford woman who was taken to the Royal Melbourne Hospital and a 26-year-old Cranbourne man who was taken to The Alfred.

A 15-year-old Narre Warren girl and a 19-year-old Narre Warren South man travelling in the Commodore escaped with minor injuries, as did a 41-year-old Karingal woman in the Statesman.

The crash is being investigated by the major collision unit.

Witnesses to the Langwarrin pedestrian death told police a blue Ford utility was travelling east on Cranbourne-Frankston Road when it struck the man, who was crossing the road with a group of friends. He died at the scene.

The driver of the utility, a 37-year-old Langwarrin man, has been interviewed by police, who are preparing a report for the coroner. The death brings to five the number of fatalities on Frankston roads this year, three of them pedestrians.

"The collisions aren't following any policeable pattern so we have to spread ourselves thin and cover every possible contingency," Sergeant Bannan said.