Jordan Hickin captured the incident as he was travelling north by Birmingham, West Midlands, on the M6 last month.
In the clip, 30-year-old Jordan from Telford, Shropshire, can be seen driving down the middle lane of the busy motorway.
In the right-hand lane three cars are driving just metres apart from each other, appearing to leave little braking distance.
As the cars overtake and pull off into the distance the first of the three cars is forced to slow to a halt because of a stationary van ahead.
The second car then goes hurtling back into the back of the first vehicle which manages to slow down and stop in time.
A third vehicle then comes crashing into the boot of the second car, causing a pile up and squashing the middle car.
Jordan said that the middle driver was left “distraught” by the accident.
He shared the video on social media last month, writing: “Sorry for the quality, cheap dashcam.
“Why do people drive so close in the third lane?”
Social media users commented about the lack of space between the cars.
Allen Henry said: “Because apparently it’s the 80mph plus lane, specifically for German cars.”
Jill Barnett said: “They just like to intimidate.”
Adam Wilkinson said: “It’s usually because people don’t keep left when not overtaking.
“People have no respect for other drivers, and force their way through.”
Dean Ison said: “Because people like to bully others in cars as they think they’re safe, they won’t do it to their face.”
And Gary Heath Pitman said: “I bet they will do it again. People don’t have a clue about safe distance.”
Speaking today, Jordan said: “I was shocked, so I pulled over. I checked they were okay then continued.
“From what I could tell, three cars started getting too close to each other. Impatience on the motorway is a killer sometimes.
“The first had to stop suddenly behind a van. The second car managed to stop in time. But the third car barely hit the brakes and the fourth car followed as well.
“The third car was squashed by the impact, a young female driver, she was distraught.”