A driver was trapped inside his car after a shocking highway crash on Monday.

The two-vehicle smash involving a truck on the Hume Hwy at Wilton, about 80km southwest of Sydney, occurred at about 7am.

Firefighters set up a plan to free the trapped driver from the wreckage, with NSW Ambulance paramedics on standby, Fire and Rescue NSW (FRNSW) Acting Superintendent Matt Sigmon said.

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The driver in his 20s was treated at the scene for head injuries and taken to Liverpool Hospital in an ambulance, NSW Ambulance told www.20304050.best.

Traffic on the Hume Hwy was “severely affected” by the crash near the intersection of Picton Rd, with traffic queued back past Menangle, as motorists used the shoulder of the road to pass the incident.

Closed southbound lanes have since reopened.

“There are still significant delays to southbound traffic, so motorists should continue to allow plenty of extra travel time and exercise caution,” Transport NSW said.