The 18-year-old pedestrian was struck by the truck on the M2 Motorway at Seven Hills, about 1 kilometre east of Abbott Road, about 2.30am.

He was treated at the scene by paramedics before he was taken to Westmead Hospital in a critical condition and later died.

The truck driver was not hurt but received treatment for shock.

He was taken to Blacktown Hospital for mandatory blood and urine testing.

Police said officers are continuing their investigations, and a report will be prepared for the Coroner.

The death follows a series of fatal car crashes on NSW roads over the past three days.

Dr Vincent Wong, 76, and a 26-year-old man died after a crash between a motorbike in Lane Cove in the early hours Saturday morning.

Superintendent David Driver said it appeared the 26-year-old motorbike rider had gone through a red light at a high speed and collided with Mr Wong's car.

In Sydney's south west on Sunday morning, a driver died after their car crashed into a tree and caught alight at Badgerys Creek Road at Bringelly.

A 17-year-old man died in hospital after a two-car crash on the Princes Highway at Wandandian south of Nowra on Saturday afternoon, and a 75-year-old man was killed after a collision on the Motorway Link Road on the Central Coast about 1pm Friday.

A passenger also died at Dapto, in the Illawarra region, on Friday after a car crashed into a tree. The vehicle caught fire and residents managed to free the driver, but the passenger was trapped and died.

Police said that more than 360 people have died on the state's roads so far this year.

On Saturday night, a P-plater was charged after he was allegedly caught street racing in western Sydney with two young children who were unrestrained in the back seat of the car.

The 33-year-old driver allegedly reached speeds as high as 120km/h in an 80km/h zone, with his wife and two children, aged three and 18 months, in the car.