As with a road or river. This usually depicts change, but sometimes with difficulties, depending on the dream. For instance if the river or bridge is difficult to cross, then it suggest you have fears or other problems to contend with in the change.
Sometimes the change is a major one, such as leaving childhood and entering adolescence, or the entering into old age. Marriage or parenthood could be such a change. Obviously, death also is frequently depicted as the crossing of a river or a threshold. See archetype of death
What you are crossing points to an obstacle you are meeting, often of a feeling nature to overcome. Maybe fear or uncertainty causes you to be unable to make the change, so you dream of a bridge giving way. Such changes often are to do with major life junctures, such as from youth to adulthood; pre-puberty to adolescent; single to married; young to middle age.
Crossing also suggests meeting the things that you do in everyday life. A busy road would indicate this, the traffic representing the many factors in life, other people’s decisions and activities, that could impact with you in one way or another. Making such crossings sometimes brings strength, or develops strength.
Something like a cable or tree trunk crossing something like a river or chasm depicts connection of some sort, something that has risk involved or needs courage to make the change.
Sometimes: A trial or test such as initiation.
Useful Questions and Hints:
What is it I am crossing, and what challenges or dangers are involved?
Am I making changes in my life at the moment, crossing from one situation to another?
If I manage to cross, what is on the other side that I wanted to reach?