The mother and father, both in their 20s, and their two daughters, who were both under three, were pronounced dead at the scene after their Fiat collided with an aggregates lorry on the A801 near Polmont yesterday afternoon.
The family are understood to have been from West Lothian. The lorry driver was shaken but uninjured, police said.
The tragedy happened near the Lathallan roundabout by junction four of the M9.
Three Scottish Fire and Rescue Service crews from Bo'ness, Falkirk and Larbert were sent to the incident and firefighters cut free one casualty from wreckage.
Sergeant Andrew Thomson, of Police Scotland, said: "This was a collision between a rigid tipper lorry and a hatchback Fiat car.
"The four occupants of the Fiat car were pronounced dead at the scene. They were a mother, a father and two pre-school children.
"The truck driver was badly shaken but uninjured.
"Our investigations are at an early stage but we are asking anyone who saw a black Fiat car or a tipper lorry on this road to get in touch."
The road, which runs from the Bowhouse roundabout near Maddiston to the roundabout which accesses Polmont and the M9, was closed for several hours while Police Scotland investigators surveyed the screened-off scene.
A series of diversions were put in place and Traffic Scotland and the AA reported severe disruption around the Polmont area at the junction with the A801 and the M9 into yesterday evening.
The A801 links the M8 and M9 and has been the scene of numerous accidents.
In 2012, MP for Linlithgow and East Falkirk Michael Connarty spoke in Parliament about the need for money to be spent making the road safer.
He said the A801 is "probably the most dangerous road in Scotland when it is not snowing". He was reported as saying he had been calling for the "desperately-needed" upgrade for more than 20 years.
He said: "Upgrading this road was one of my first campaigns as an MP in 1992. It stuck out like a sore thumb as a missing link in the road network."
"There have been many bad accidents on this road. If you don't know the area, the dip can be very deceptive."
A local farmer said: "It's tragic, especially since a young family was involved."