A young man has died after he crashed into a fence while driving along an unmarked Sydney road overnight.

The 19-year-old P-plater was driving a ute along Ninth Avenue in Llandilo, Penrith, about 8pm when he apparently lost control.

The ute left the road and crashed through a tall metal fence.

Paramedics tried to revive the man but he died at the scene.

Resident David Harding was first on the scene after hearing the crash from his home.

“I heard a big bang, I thought something might’ve fallen in the garage,” he told 9NEWS.

After spotting smoke from the crash, Mr Harding ran to the wreckage and found the victim.

“It was pretty scary to see someone in a lot of pain,” he said.

“I don’t think there was a lot anyone could do, we didn’t want to try and move him because if he’s got an injury to his back or his neck or something like that.”

Mr Harding called Triple Zero and said “it was only a few minutes and then emergency services arrived”.

He said the road should be upgraded to avoid future accidents.

“We’ve got four young children here, and we often see police pulling over (cars) in the evening,” Mr Harding said.

“I believe there’s too many cars travelling down the street at excessive speeds, there’s no line markings further up the road, so they need to do some improvements to make it safe for anyone.”

Distressed family members are believed to have been at the scene of the crash, comforting one another.

A friend today told 9NEWS the victim was a happy, well-liked person.

It is understood that sections of Ninth Avenue are unmarked, and that recent calls to update it with white markings were shut down by the local council.

A young has been killed when his car left the road and crashed into a metal fence. (9NEWS)