If you have already contacted the media without success it may be that your issue just isn't considered as important to others as it is by you.
If that is true, why put yourself through the hassle of climbing a bridge followed by the hassle of dealing with the authorities afterward? If the issue doesn't matter now, then you'll just be some guy who climbed a bridge for an issue that doesn't matter.
You should consider finding a way to learn of others that are interested in whatever it is that is bothering you and when there are enough of you the media will want to listen. You will get better coverage if the media is truly interested in what you have to say and not just listening because your issue is associated with some action that overshadows it.