Поставить предлог или послелог если требуется : ... spite ... in the heavy traffic I got there ... an hour.

In spite of the heavy traffic, I got there in an hour. - Несмотря на интенсивное движение, я добрался туда через час.

The complex preposition “in spite of” includes the preposition “in” and the postposition “of”. The preposition “in” before “the heavy traffic” is not needed. The preposition “in” before “an hour” is required to make the sentence meaningful.