近道 and 遠回り: a shorter route and a detour
Compare a shortcut through a park with a detour to a bridge, separating route length from access conditions and travel time.
A shorter way to a destination
近道, read ちかみち, means a shorter route to a destination. 公園を通ると駅への近道になります。 says that going through the park provides a shortcut to the station.
近道を教えてください。 asks someone to identify a shortcut. The destination must be understood before shorter and longer routes can be compared.
Taking a roundabout route
遠回り, read とおまわり, means taking a roundabout route. 橋まで遠回りして川を渡りました。 says that someone detoured to the bridge and crossed the river.
工事のため、遠回りしました。 says that someone took a detour because of construction. 工事のため gives the reason without specifying the extra distance or arrival time.
Separating distance from access conditions
この近道は夜には通れません。 says that this shortcut cannot be used at night. Being shorter does not establish that a route is always available.
少し遠回りですが、この道のほうが歩きやすいです。 says that this route is slightly roundabout but easier to walk. Greater distance and easier walking can coexist.
Does calling a route 近道 establish that arrival is always faster?
Show the answer and why
No. It identifies a shorter route. Access, walking conditions, and actual travel time need separate information.