Hmm... I would drive across a bridge meaning its length. I would walk across the road if I wanted to get to the other side. I would walk along a road if I were heading in the same direction it is.We drive across a bridge and we walk across a road.
Yes, you can.If I started on the south half of a bridge and finished on the other side, can I say "I walked across the bridge".
You can use "I walked across the bridge" whichever side you start from.Is it different from starting on the south side to the north side?
'Across' gets to the other side. You could walk along a bridge if you were, for example, taking photos of the river or the town. You stay on the bridge but move from one part of its length to another. Or there might be paper lanterns strung along the bridge: these aren't moving to the end to get off it.