Laigh Milton viaductGatehead, East Ayrshire
This viaduct was opened in 1812 as the first ever railway(?) viaduct on this planet.
Built by the Kilmarnock and Troon Railway for the Duke of Portland it worked very well but of
course was a few years earlier than the invention of the steam locomotive.
As you can see the wagon's flat wheels ran outside the vertical plates of the trackway and
on the flat tracks.
From that you can see that on bends the wagons were guided by the inside
vertical plate and the outside vertical plate would have had little effect.