Walking the bridges

Here's something that crosses my mind every time I drive over a bridge around here.

Is there some kind of law or requirement on the SC books that specifically requires bridges to have sidewalks? There are lots of bridges around here that have sidewalks on them, which is very nice.

The only problem is that for a lot of these sidewalked bridges, there are no sidewalks that lead up to the bridge.

So you can walk the bridges in relative comfort. You just have to rough it or put on your hiking boots to get there though.

What's up with that?