The New York Times Magazine looks at impulsive suicides. Apparently, just creating small obstacles to suicide can produce dividends; In Britain in the 1970s, they switched from coal gas to natural gas, which has very little carbon monoxide, and suicides fell by 1/3. The article's purpose seems to be to refute the "they'll just find another way" opposition to suicide barricades on bridges. They also suggest that keeping guns locked up, with ammunition in another room, may give a suicidal person just enough cooling off time, though this is undermined by the fact that the suicide survivor quoted in the article had to go out and purchase the gun she used.

The most interesting thing I found in the discussion about the difference between impulsive and planned suicides, is that those whose suicide is preceded by well-documented mental illness and multiple warning signs choose hands-on methods, like pills and slitting wrists, while the impulsive choose to jump from great heights or use a gun. Yet it is the impulsive methods that are most successful; "The natural inference, then, is that the person who best fits the classic definition of 'being suicidal' might actually be safer than one acting in the heat of the moment — at least 40 times safer in the case of someone opting for an overdose of pills over shooting himself."

I, personally, was of the "they'll just find another way" mindset on bridge barricades, but it makes sense that one might impulsively jump to one's death. I am not in a habit of randomly falling over in my day to day life, but I'm always convinced, when I find myself near a railing, I'm somehow going to accidentally clear the jump and plummet to my death. I have dreams where I'm up at a great hight and resort to crawling on all fours to avoid falling, and I still manage to take a fall. More a fear of heights than suicidal impulse, but it still helps me understand how such things happen.