HFF!

It would appear that the sequence of events is this:
1) Something in front of the orange truck slowed down suddenly.
2) The driver of the orange truck braked hard, and steered toward the hard shoulder to avoid a collision. (Note this truck is very lightly loaded, and can therefore stop easily)
3). The red truck, being an artic fully loaded with roadstone. could not stop in such a short distance, and hit the rear of the orange truck pushing it through the barrier.