Nothing says “Which way” like a bridge. Of course, bridges are inherently limiting. You can’t go any which way. You can go there. Or you can go back the other way. Going off the sides are frowned upon in most situations.
Sometimes, you can throw a fishing line off the side of a bridge. Catch a trout or something like that. Other times, it’s a long, long way to the water below.
And sometimes, bridges don’t span water. They span canyons and other hard surfaces — roads and traffic and such.