A truck has crashed on the Great Western Highway near Explorers Tree at Katoomba at about 6.30am on Tuesday, September 15.
One westbound lane is closed, with police directing traffic.
The driver sustained minor injuries.
Emergency services, a heavy vehicle tow truck, heavy vehicle inspectors and Transport for NSW are at the scene.
Live Traffic has described the traffic conditions as "moderate" and to allow extra travel time.
At 9.30am Live Traffic advised the highway would be closed for about 20 minutes while recovery of the truck takes place.
At 2pm, Live Traffic advised there were still heavy traffic conditions, with one westbound lane still closed. Some buses have been delayed by 45 minutes.