to be on the safe side

We use this expression to say someone should do something just to be sure there will be no problems - normally with time or quantity.

我们用这个短语来表示某人在确保没有问题的条件下去做某事——通常是时间或数量上。

A: Is it an expensive restaurant we're going to?

我们要去的这家餐厅贵吗?

B: No, but I'm taking 50 to be on the safe side.

不贵，但为了保险起见，我要带上50元。