Comment by jonas21

This is all private money. If these companies didn't spend the $100B developing autonomous vehicles, it wouldn't suddenly be available for building public transit.

Beyond that, $100B doesn't go as far toward building transit as you might expect. For example, San Diego recently spent $2.3 billion on a light rail extension that's projected to have 34,700 daily trips by 2030. If you assume most of these are round-trips, it's serving fewer than 18,000 people. Spending $100B at this rate would serve around 750,000 people (0.2% of the U.S. population).

The most cost-effective form of public transit in most places is busses because they can reuse existing road infrastructure, and in the U.S., labor accounts for around 70% of the cost of operating busses. As a result, autonomous driving technology should be helpful in scaling public transit systems as well.