I agree with the author of this series of articles (I & II). Signs suggesting that folks prepared to jump from a bridge should call a suicide hotline are not going to change the death toll. You can park your ambulances down stream and pluck the dead and dying from the waters or you can do all you can to prevent them from jumping. A part of that are preventative barriers. A part of it is pushing suicide prevention (making access to mental health care readily available, hotlines, working to decrease stigma attached to seeking caring, etc) before these folks get out onto the bridge.
Awareness is key. (Thanks for the links, Randy)