Scotland’s Forth Bridge may be the most famous railway river crossing in the world, but there is another, equally important, if not quite so grand affair spans the same river, a little further upstream. Now the Forth Viaduct at Stirling, where the Highland Main Line to Perth, and the Kincardine branch to Alloa cross the waters of the River Forth, has been given an engineering facelift, just like its big, red brother downstream.