They maintain, improve and upgrade every aspect of the railway infrastructure, including: the track, signalling systems, tunnels, level crossings, stations, etc.
Nhw sy’n cynnal, gwella ac yn uwchraddio pob agwedd ar y seilwaith reilffyrdd gan gynnwys y trac, y systemau signalau, twnelau, y croesfannau, y gorsafoedd etc.