specially upgraded high-speed lines which have special features as a result of topographical, relief or town-planning constraints, on which the speed must be adapted to each case.
ar línte ardluais arna n-uasghrádú go speisialta a bhfuil gnéithe speisialta acu de bharr srianta topagrafacha, srianta a bhaineann leis an rilíf nó srianta pleanála bailte, agus ar gá an luas a oiriúnú orthu do gach cás ar leith.