 The loch existed during a brief period (some 900-1,100 years in duration) of climatic deterioration, during a much longer period of deglaciation, subsequent to the last main ice age (The Devensian).From a distance they resemble man-made roads running along the side of the Glen, hence the name.The glen runs north from Glen Spean which takes the main A86 trunk road and the railway of the West Highland Line, both running about a further southwest via Spean Bridge to Fort William.