safest

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

最安全的办法是在后相当一段距离, 防前的汽车突然停车。

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

最安全的方法就是和前的车适当的距离, 免它突然刹车。