John Lott would appear to be in Japan, and has a very interesting observation:
A very common way of people committing suicides is for people to throw themselves in front of trains. I can only imagine the social costs of this form of suicide in that the trains appear to be stopped for an hour or so. It would be interesting to compare the costs of say Americans committing suicide with the cost of Japanese.
In the United States, someone determined to kill themselves will likely choose a firearm. It would appear that in Japan, throwing oneself in front of a train is how they get the job done. Also of note is that Japan’s suicide rate is much higher than the United States, despite a near prohibition on firearms.
I have little doubt that the availability of firearms increases the rate of suicide by gun in the United States. I have my doubts, however, that it is a primary driver of suicide rates overall.  As the Japanese show here, there are plenty of substitute methods that are just as sure and swift.
I think a few Japanese suicides still involved the old method of cutting their stomach out with a knife.
However, I think more suicides are performed using small hibachi grills. A person seals themselves in a room or car, lights the hibachi and lets the fumes suffocate them.
Even more disturbing is/was the trend of group suicide where several people gather together and use the hibachi-suicide method. They are/were basically strangers who meet on the internet and decide to kill themselves. (There was an episode of Paranoia Agent that showed this, if you watch Japanimation.)
(If you’ve ever taken the rail line around the NY area, trains are sometimes cancelled due to suicides.)