The 1878 official opening of the first Tay Bridge was marked by a train load of dignitaries crossing at the impressive speed of 40km/h. A century and a quarter later, this is roughly the same pace at which today's trains are allowed to cross the new bridge. The intervening period has seen the slimline old bridge collapse, a new structure built partly from the original's remains, and then this crossing itself fall into 'disrepair', forcing the refurbishment contract.
At around 8pm on storm strewn 28 December 1879, the collapse of the original 18 month old bridge's central navigation section, killing all 73 occupants of a crossing train, marked the birth of much more stringent bridge design standards, especially for live loadings. The new crossing, started four years later, boasts a 2.7kN/m 2wind loading - over five times that of its predecessor - plus reuse of numerous undamaged original trusses.
These slender trusses form the outer two of the current bridge's four truss deck section, spanning twin column piers over twice the width of their predecessors.