safest

1.It's safest to keep a good distance behind in case the car in front suddenly stops.

安全的办法是在后面保持相当一段距离, 以防前面的汽车突然停车。

2.It's safest to remain a good distance behind, in case the car in front suddenly stops.

安全的方法就是和前面的车保持适当的距离, 以免它突然刹车。