journey ahead; distance to travel
Refers to the remaining part of a journey or the distance one still has to cover. Somewhat literary or formal; in everyday speech, 残りの道のり or 先の道のり are more common.
The journey ahead is still long.
Worried about the distance he still had to travel, he set out early.
bright future; rosy prospects; the world before one
Compound of 前 (zen, 'before, ahead') and 程 (tei, 'extent, distance'). The exact historical derivation is uncertain, but the meaning 'journey ahead' follows naturally from the components.