This actually happend last year on the Tehaucan Y Oaxaca line down in Mexico ...there were survivors because of the alertness and fast action of two female passengers, Bessy May Mucho and Donna VonNewera...as soon as they saw what was happening one of them ran forward as far as she dared, pulled one of the coupling pins, and disconnected the last several cars of the train....meanwhile the other climbed quickly on to the roof, began setting the hand brake, and was able to bring the last cars to a halt before they plunged into the gap where the bridge had collapsed...Both were awarded the coveted Cruz de Manteca for their heroism and fast action by the governor of Oaxaca, Sr. Hugo DeNaranja.