Five members of a family who fled Afghanistan to find a new life in Australia are dead after a horrific crash on "a shocking day" on NSW roads.

The 23-year-old mother tried to shelter her child as their Toyota Camry veered into the path of a water tanker on Picton Road near Wilton about 8.20am yesterday.

"It's something that no humans should have to see"... police at the crash scene near Wilton in which five people died. Credit:Ken Robertson

The truck, which was travelling about 100km/h, crushed their car.

Her husband and two sisters were also killed.