The company completed construction of two lines, The first, opened in 1877, was approximately long, running south-east from a junction with the London and North Western Railway's Caernarfon to Afon Wen branch at Dinas Junction, to Bryngwyn. There were intermediate stations at Tryfan Junction and Rhostryfan. From Bryngwyn, a shallow incline climbed the northern flank of Moel Tryfan. From the top of the incline a number of quarry tramways connected to the Alexandra quarry, Moel Tryfan quarry, Fron quarry, Braich quarry and Cilgwyn quarry.