Three men believed to be in their late teens and early 20s have been killed after their car and an articulated lorry collided.
A third person was taken to hospital with serious injuries following the crash on the A10 near Turnford, a spokesman for Hertfordshire Police said.
The accident happened on the northbound carriageway at around 2.15pm when a Vauxhall Corsa collided with the Mercedes Artic lorry.
The driver and two passengers in the Corsa died at the scene while a third passenger was taken to the Royal London Hospital, Whitechapel, by air ambulance with serious injuries.
The driver of the lorry was not injured.
More top news
Scotland finally injected some momentum into their World Cup preparations as they beat Italy 48-7 triumph at Murrayfield.
Labour leadership candidate says Britain playing its role in the migrant crisis would help Cameron secure the promised reforms in Brussels.
Ten people have been taken to hospital and another two treated for injuries after a bus crashed into a tree in east London.