The user is not prohibited from moving in the opposite direction; the arrow merely indicates the direction in which the user is likely to want to go.
值得注意的是这些箭头不似那些用来单行道的箭头，而更象超级市场里指示食品部的那种箭头。 因为指示箭头的目的不是禁止用户向别处同行，而是仅仅说明用户想要行动的方向。
The arrow indicates direction of sediment transportation.
电力线上的箭头表示所要画的切线方向。
The arrow indicates direction of sediment transportation.
电力线上的箭头表示所要画的切线方向。
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