32,000 deaths a year from driving in US. 500,000 deaths a year from cancer in US.
If it was me investing, I'd put my money into solving the cancer issue. Even if you can shave 5% off that death toll, you've already done more than eradicating cars would.
The problem is driverless cars sounds like awesome fun. Solving cancer is the harder problem.
I mean, I'm not saying your point is invalid, or that trying to extend our lives by fighting the 'old age' diseases is without value, but I do think that the number of deaths does not tell the whole story.
My personal favorite:
http://en.wikipedia.org/wiki/List_of_countries_by_suicide_ra...
Suicides at 11.1 per 100,000 per year, or about 33000 per year. You're roughly as likely to kill yourself as to die in an auto accident.