为了缓解交通拥堵，这座城市正在将主干道从两车道拓宽为三车道。

The city is widening the main road from two to three ___lanes to ease traffic.

在变道至快车道之前，务必检查后视镜。

Always check your mirrors before changing to the fast ___lane.

在一些城市，公交车被允许在高峰时段使用一条额外的车道。

In some cities, buses are allowed to use an extra ___lane during rush hour.