 Derwydd Road at 229 feet is the third highest point on the Central Wales Line.The Pontardulais to Swansea line was undulating with stiff alternating gradients; Dunvant was approached by miles at 1 in 72 eastbound and two miles at 1 in 70 and 1 in 80 westbound.The Carmarthen line was gently graded all the way.