if we divide each of those percentages by 50, we should come up with the odds of dying in a given vehicle per year,

I'm being very nitpicky but this isn't quite how it works, if you have a 90% chance of survival one year, you'd have 0.9^2 = 0.81= 81% chance of surviving two years in a row. With that in mind, the odds of dying should be relative to the fiftieth root of surviving fifty years, which gives:

• Motorcycle: 0.478%
• Car: 0.151%
• Ferry: 0.065%
• Amtrak: 0.0086%
• Airplane: 0.0014%

Without additional decimals it's hard to see the change for the really small numbers but it doesn't make much of a difference in reality.