When a truck collides with a smaller vehicle, it is highly likely that the smaller vehicle will suffer the most damage and that the people inside that vehicle will suffer the worst injuries. This is simply due to the inherent nature of larger trucks. They carry more weight and thus maintain their momentum far easier than smaller vehicles. They also make a greater impact when they collide with any object.
As such, when trucks are involved in accident, the people who are hurt usually suffer terrible, catastrophic, or even fatal injuries. Traumatic brain injuries are common, as are permanent injuries to their spinal cord which could cause paralysis. The victims of a truck accident could also suffer a wide range of serious bodily injuries, such as broken bones, severe burns, and injuries bad enough that they require amputation.