1pm: Both southbound lanes of the M1 Princes Motorway have reopened after an earlier crash involving a car and truck at the base of Mount Ousley.
Both vehicles are now on the centre median.
Southbound traffic remains heavy and is queued about 2km.
Motorists should continue to allow plenty of additional travel time.
Meanwhile, two of three southbound lanes are still closed on the M1 Princes Motorway at Waterfall due to flooding.
12.50pm: The M1 Princes Motorway remains closed southbound at the base of Mount Ousley following a truck and car crash.
Light vehicles are being diverted onto Mount Ousley Road while heavy vehicles are being parked on site.
Southbound traffic is queued about 2km and motorists have been told to avoid the area or allow plenty of additional travel time.
Emergency services and traffic crews are on site.
Meanwhile, two of three southbound lanes on the M1 Princes Motorway are closed near the Princes Highway at Waterfall due to water on the road.
12.30pm: Emergency services are working to free one person who is trapped following a crash between a car and a truck on the M1 Princes Motorway at Mount Ousley.
Emergency services were called to motorway, near the Mount Ousley Road exit, just after noon.
A NSW Ambulance spokesman said paramedics were assessing one person.
The spokesman said initial reports suggested that person was a female and she was trapped inside one of the vehicles.
The motorway has been closed southbound, with light vehicles being diverted onto Mount Ousley Road.
12.15pm: An accident involving a car and a truck has closed the M1 Princes Motorway southbound at Mount Ousley.
Light vehicles are being diverted onto Mount Ousley Road.
B-doubles are unable to pass the accident scene and are being parked.
More to come.