This happens a few times a year on Caltrain (San Jose, CA to SF, CA). And of course it is a VERY regular occurrence in Tokyo where I am right now -- so regular, in fact, that the railroad companies bill the families for the delay costs in an attempt to prevent it. The hypothesis is that in Japan, where families are very important, no one would want to put their family deeply in debt as part of a suicide. The hypothesis has been proven wrong many, many times, almost on a daily basis.