The Hume Highway is closed to traffic heading northbound between the Illawarra Highway exit and New Berrima, following a single vehicle accident late this morning.
A truck carrying crusher dust in a dog trailer was forced to take evasive action when a vehicle emerged from Golden Vale Road.
The trailer flipped, but has since been righted.
Hume Police say they are expecting the lanes to open within the next hour.
In the meantime, the shoulder is open to heavy vehicles only, while cars are being diverted via the Illawarra Highway through Moss Vale and back onto the Hume Highway north of Berrima.
Motorists are advised that traffic is heavy through the diversion area.