At an intersection with one lane in your direction, which action by the vehicle ahead prevents you from passing it on the left?

Passing at intersections is not always prohibited, but a single-lane left-side pass requires the right vehicle status, enough room and safety.

路口並非在所有情形下都禁止超車。單車道內從左側通過須滿足前車狀態、空間和安全等條件；前車示意左轉時不可這樣做。