Guardrail, guardrail terminal, and support post designs that improve control of a vehicle during collisions are described. The disclosed designs also reduce the likelihood of intrusion into vehicle systems and the occupant compartment(s). Embodiments include folding and/or flattening of the guardrail and controlling the folded and flattened guardrail to avoid intrusion into the vehicle. Other embodiments include containing the guardrail in an impact head of a guardrail terminal, which also avoids vehicle intrusion.