Complex sentence: Owing to the difficult terrain in the area, the line from Glasgow, to the south, enters from the northeast and trains from Glasgow to Mallaig, the terminus of the line, have to reverse at Fort William railway station.
Split into simpler sentences: Owing to the difficult terrain in the area, the line from Glasgow, to the south, enters from the northeast. Trains from Glasgow to Mallaig, the terminus of the line, have to reverse at Fort William railway station.