Complex sentence: The train entered the overrun tunnel, throwing up sand from the drag; when the driver's cabin made impact with the hydraulic buffer, the carriage was separated from its bogie and the coachwork was forced into the end wall and the roof.
Split into simpler sentences: The train entered the overrun tunnel, throwing up sand from the drag; when the driver's cabin made impact with the hydraulic buffer, the carriage was separated from its bogie. The coachwork was forced into the end wall and the roof.