Van driver is charged after allegedly hitting a teenager - throwing him into a brick wall 20 metres away and leaving him fighting for life

A van driver who allegedly struck a teenage pedestrian so hard he was flung 20 metres has been charged while the boy he hit fights for his life.

The 17-year-old was walking with a friend on the footpath before he was allegedly thrown into a brick wall by a grey Kia Carnival on Thursday by a van police say veered across three lanes of the Hume Highway at Casula, south-west Sydney.  

The driver, 37, from Leppington, was tested and later charged with dangerous driving occasioning grievous bodily harm and negligent driving occasioning grievous bodily harm. 

Teams of paramedics and police work to save a teenager who is fighting for his life after a van allegedly slammed him into a brick wall at Casula on Thursday

The teenage victim was allegedly thrown into the air and hit this brick house (pictured, left) from the footpath by the impact of the collision beside the Hume Highway

The man, who was unharmed, was refused bail and also had his licence suspended at Liverpool Police Station.

Police said he returned negative tests and is due to appear in Parramatta Local Court on Friday.

The teenage victim is in Westmead Hospital with serious head and leg injuries in a critical and unstable condition. 

Multiple teams of paramedics and a dozen emergency workers had to navigate the busy road to save the badly injured boy and carefully get him to Westmead Hospital.

The incident caused chaos on the Hume Highway for hours.

Police say investigations into the circumstances surrounding the alleged horror crash are continuing. 

The damage done to the Kia Carnival at the scene of the alleged incident 

More carnage at the accident scene beside the Hume Highway where a teenager was allegedly struck by a car on the footpath and slammed into a house