Emergency services were called to Wilberforce Road, near Freemans Reach Road, just after 4.30am to reports of a two-vehicle collision between a hatchback and a lorry.

It was learned that the hatchback driver, thought to be 19 years old, was found dead at the scene.

He has not yet been officially identified.

The driver of the truck, which included the dog, escaped uninjured in the accident.

Police said he was taken to Nepean Hospital for mandatory testing.

The crash caused the closure of Wilberforce Road in both directions between Freemans Reach Road and Rose Street, according to Live Traffic NSW.

Motorists are asked to avoid the area and allow additional travel time while police direct traffic at the scene.

Light vehicles and trucks can use Freemans Reach Road and Kurmond Road in both directions, while B-doubles must park.

A crime scene was established while police investigated the circumstances surrounding the crash.

Police will prepare a report for the coroner.

Anyone with information about the collision is asked to contact police via Crime Stoppers on 1800 333 000. online.