Complex sentence: South of the Aberglaslyn Pass, the railway will pass over the new Nantmor road bridge before calling at Hafod-y-Llyn halt shortly before the line leaves the Snowdonia National Park.
Split into simpler sentences: South of the Aberglaslyn Pass, the railway passes over the new Nantmor road bridge before calling at Hafod-y-Llyn halt. Shortly afterwards, the line leaves the Snowdonia National Park.