I think what you're describing is insurance, not taxes. I'm sure almost all auto insurance is paid by taxpayers, too, but I wouldn't call auto insurance a tax
That's true but it's also true that studies like this one, which are true on average of the population, are often not true for each individual. It's worth pointing out that it doesn't apply to everyone.
According to the Denver city data, there were 19 murders in the Denver city area through May last year, and 11 this year. That's better, but implying that to be a statistically significant phenomenon related to marijuana legalization seems intellectually dishonest. Especially when the overall crime numbers for more common crimes don't seem to show any consistent patterns.
Also, there will be a long lag time from when driverless cars are introduced into the car-sharing market to the time that everyone is comfortable using them and there are enough to saturate the market. In the meantime, you'll be able to choose between the different options via Uber.