There seem to have been two separate person under a train incidents on the London underground today. I know nothing about either of them, but there was also one last Friday - and the cluster of events, well, first it made me feel awful, but then I wondered if there were any stats to help understand how common these events are.
Well yes there are. For example you can see some old-ish data for 1998-2005 here. I couldn't find any more recent data - you could file an FOI request if you like. BUT - TfL's twitter feeds tell the public whenever travel is disrupted. And since they use the standard form of words, it's quite simple to go through and find all occurrences, for example, for 2013 so far. So here they are:
date,lines 2013-01-15,northern 2013-01-28,district+hamandcity 2013-01-29,central 2013-02-03,northern 2013-02-10,piccadilly 2013-02-15,central 2013-02-16,victoria 2013-02-25,circle+district+hamandcity 2013-03-07,bakerloo 2013-03-10,jubilee 2013-03-14,victoria 2013-03-26,victoria 2013-04-05,central 2013-04-09,circle+others 2013-04-09,central
Fifteen in total, so far for 2013. Roughly one per week. This is not the same type of data as the old data I linked above (it includes fatalities and nonfatalities, I expect, whereas the old data is just for the former).
You can do some basic statistical modelling on this: if you assume these are independent events and model them with a Poisson distribution, then you find the probability of seeing two-or-more incidents on one day is 1.04% - which essentially means there's nothing particularly weird about seeing it happen at some point over the past three-and-a-bit months.