To highlight how dependent they might be on a key employee, businesses are often asked what they would do if that employee were run over and killed by a bus (e.g. the Bus Test) - and the answer would point out various problems for disaster recovery and business continuity planning issues.
So what are the odds of someone being killed by a bus? For the UK, we can look at the official statistics (Department for Transport).
For 2004, there were 121 accidents involving buses and causing a death. That doesn't quite mean that 121 people were killed by being hit by a bus as it would include any accident involving a bus where any number of people died (there's a table showing that 3 bus drivers and 17 bus passengers were killed).
This is expressed as a rate per 100 million vehicle kilometres of 2.3. So, on average, any one bus is involved in a fatal accident every 27 million miles of travel.
So, if we assume that there were at most 121 cases of someone being killed by being hit by a bus and if we assume that everyone in the UK (60 million people) has an equal chance of this happening then the odds are something like 2 in a million (per year).
Of course, anyone wandering around in China with their iPod on may have a higher chance.