Industrial design to the rescue!
Why dont’ they just hire some professional cowboys and wrangle them little doggies!
Actually, there is a non-lethal “goo” that’s been developed that freezes people right in their tracks and can only be dissolved with certain chemicals, however it won’t attach to someone like Spidey’s webbing rope. Some type of device is not the solution here, better bridge architecture is. The reason people jump off bridges is that it’s dramatic and they know that it’s very hard for someone to stop them.