Two teenage boys have been killed and another seriously injured in a crash in Sydney's northwest, with three people also killed in crashes on regional NSW roads.
Emergency services were called to Windsor Road at McGraths Hill about 9.40pm on Monday after reports a Nissan 200SX sports car had hit a power pole.
Two 17-year-old boys, who were passengers, were critically injured and died at the scene, police said.
The P-plate driver, also 17, was treated by paramedics for chest and internal injuries before being taken to Westmead Hospital, where he is reported to be in a stable condition.
Police were told the car carrying the teenagers lost control before striking a Ford Falcon from behind and leaving the road before hitting the pole.
Crash Investigation Unit commander Jason Hogan said police had been advised that speed might have been a factor in the crash.
A man and woman also died in a separate crash on the Sturt Highway at Hay, in the state's southwest, on Monday.
A sedan and a semi-trailer collided, with the 71-year-old male driver of the car and his female front seat passenger both dying at the scene.
A rear male passenger of the sedan was airlifted to Royal Melbourne Hospital in a serious condition, while a second rear passenger, a 23-year-old woman, was taken to Hay District Hospital with serious injuries.
The sedan was doing a U-turn in front of the truck, whose driver unsuccessfully tried to take evasive action before the collision, police said.
The truck driver, a 27-year-old man, was treated for minor injuries and taken to Griffith Base Hospital for mandatory testing.
In a third incident on Monday, a 77-year-old man died following a two-car crash on a main street at Cowra, in the state's central-west, shortly before 3pm.
The driver of a station wagon died at the scene while the other driver, a 56-year-old man behind the wheel of a Nissan Pathfinder SUV, was treated for head injuries and airlifted to Westmead Hospital in a serious but stable condition.
Police believe the Pathfinder crossed to the wrong side of the road before colliding with the other vehicle.
Further investigations will be carried out when the driver is discharged from hospital.
On Tuesday morning, a stolen tip-truck collided with another truck at Berkshire Park, north of Penrith in western Sydney, leaving both drivers seriously injured.
NSW Police acting Assistant Commissioner Anthony Boyd said all of the incidents over the past 24 hours were linked to driver behaviour and he urged people to take care on the roads.
"They are not related to any other factor except people making poor decisions," he said.
"Your behaviour whilst you are driving a motor vehicle is your responsibility.
You will be held accountable when you are driving in a manner which is dangerous."
The state's road toll has soared in the past 12 months, with 358 people killed in the year to Monday.
That tally was well up on the 273 people killed in the corresponding period a year earlier.
