Dashcams are slowly becoming popular in many places outside of Russia and I approve of this message. Especially if you live in a sue happy country and/or a police state. Having a silent witness to what had happened could save your entire future.
This video was filmed on I-15 Interstate in Las Vegas, Nevada. The car with dashcam passes a flatbed truck, moments later the truck cuts right in front of it, missing it by maybe two feet as its trailer jackknifes.
After a bump into the concrete barrier, the truck bounces back and cuts across all lanes, narrowly missing a van that skillfully managed to dodge it, but hit an older model pickup truck.
I think the reason for jackknifing was sudden and abrupt braking. You can see that the traffic was slowing down due to an obstacle ahead. The truck driver had speed and a pile up of cars in all lanes required him to start braking rapidly, but he may have overdone it.