A recent theory regarding the collapse of the Tay Bridge suggests that as the passenger train crossed the bridge very high winds on the night caused the train/carriages to lift off the rails. The wind blew across the top of the train easily. However, because of all the mechanical devices (such as wheels etc...) under the train, the wind beneath slowed down. Consequently, the train began to lift - in the same way as a wing on an aeroplane. The train became de-railed and then hit one of the sides of the bridge as it continued to travel forwards. This gave the whole structure a sudden shock.

The shock of the crash sent a 'shock wave' down the entire structure and the wrought iron ties pulled away from the cast iron 'lugs' at the bottom of the cast iron columns. Cast iron is very brittle and cracks under tension whilst wrought iron is very durable. This design flaw in the use of materials with different properties led to the collapse of the Tay Bridge.

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