straight road; direct route; journey; voyage
Noun use; can refer to a literal straight road, a direct route, or a metaphorical journey. The 'voyage' sense is somewhat literary.
He headed straight for the airport.
I push forward single-mindedly aiming for success.
If you go straight along this road, you'll reach the station.
Life is a long journey.
bon voyage; have a safe journey
smooth sailing; everything going well
path of sincerity; single-minded devotion to truth
Compound of 一 (one) and 路 (road, path). The adverbial use developed from the idea of a single, undeviating road.