Tay Bridge disaster warned of their unreliability, and declined to estimate conditions at Dundee from readings taken elsewhere. One modern interpretation of available information suggests winds were gusting to . Usage of the bridge was restricted to one train at a time by a signalling block system using a baton as a token. At 7:13 p.m. a train from the south (consisting of a 4-4-0 locomotive, its tender, five passenger carriages, and a luggage van (brake van) slowed to pick up the baton from the signal cabin at the south end of the bridge, then headed out onto the bridge, picking up speed.
Tay Rail Bridge Bouch had used the technique for viaducts including the Belah Viaduct (1860)) on the South Durham & Lancashire Union Railway line over Stainmore, but for the Tay Bridge, even with the largest practicable caissons the pier dimensions were constrained by their size. Bouch’s pier design set six columns in a hexagon maximising the pier width but not the number of diagonal braces directly resisting sideways forces. The engineering details on the Tay Bridge were considerably simpler, lighter, and cheaper than on the earlier viaducts. On these the machined base of each column section docked securely into a machined enlarged section