With the increased weight of engines and coaches necessarily came a strengthening of the road. The rebuilding of the old wooden bridges has already been noted, but some of the girder bridges have been rebuilt also, the last of these, over the Severn at Kilkewydd, near Welshpool, having only been completed last year. This is now a fine structure of four clear spans of more than 60 feet, supported by concrete piers and abutments. Then, too, for the light iron rails laid on a sandy ballast of the old days there have been substituted 80 lb. steel rails laid on broken granite ballast, with a corresponding strengthening of the fastenings, sleepers, etc., and to expedite the running of non-stop trains, mainly during the pressure of the tourist season, special appliances have been erected at wayside stations for the exchange of the "tablet," by means of which the working of a single-line railway is controlled, additional passing places have been constructed, station platforms in several cases considerably lengthened, and one or two new stations opened, bringing the total on the system up to 100. During the war when Park Hall, Oswestry, was converted first into a vast training camp and later, in part, into a German Prisoners of War camp, a large amount of military transport work fell to the Cambrian, a network of sidings being constructed through the area occupied, and about a quarter of a million of troops were carried over the system to and fro, an additional strain on the human and mechanical resources of the Company which, however, was most efficiently sustained.