bridges, tunnels

According to the Metropolitan Transportation Authority, there were 702 cases of people on the tracks between 1990 and 2003. Over half of them resulted in deaths.

Now, why do we worry about making bridges harder to kill oneself with when the subway will to it for you with such regularity? Seriously though, it's one of those "what exactly bunches the undies?" questions.

Is it because the bridges are also thought of as things of beauty that we're so worried about alternative uses whilst the subway is underground and animal like? more dangerous feeling? I dunno. Seem to me they're both key transportation elements.