Suicide Barriers' Effectiveness

This paper looks interesting:

With support from mental health workers, elected officials, the California Highway
Patrol, and the local community, Caltrans has announced their intention to install a
suicide prevention barrier on the Cold Spring Bridge by 2010 at a cost of $605,000.
During the course of the debate a number of people have claimed that such a barrier
would not only deter suicides at the Cold Spring Bridge, but actually prevent suicides and
thus save lives. This claim is unfounded. A review of the evidence presented in favor of
building the barrier and my own research reveals that there is no evidence that installing a
suicide prevention barrier on the Cold Spring Bridge would save lives.

Hat tip to Andrew Gelman's site. These seem like a monumental waste of money, even a priori without seeing this paper. Why? Because at best you would expect the potential suicider to substitute towards the cheaper location, not stop altogether. Since suicide locations are probably supplied in huge quantities to every market, you've really not imposed any meaningful deterrence. As Gelman points out on his blog, a reduction in suicides at a certain location is not the same thing as a reduction in suicides in aggregate.