In the world of dreams the rules of reality do not necessarily apply. Each dream is unique and it's a direct link to the soul and spirit. Psychology provides its own theories on what dreams mean, but so did tradition and the study of dreams for thousands of years before any relevant science had developed.
Dream Meanings - Bridge
If you dream that you are walking on a bridge, you will have success. If you are building a bridge this means that, after some effort, you will be vindicated. If you see a bridge being knocked down, take care at work because a wrong move could be damaging.