allow for

1. 考虑到

We'd better start earlier. We should allow for traffic delays.

我们还是早些动身为好。我们要考虑到路上交通会有耽搁。

allow of

1. 容许有……的可能

The task is so urgent that it allows of no hesitation.

任务非常紧迫, 不容迟疑。