If gridlock is a major issue now, self-driving vehicles won't help in a major way, since you still need X square feet to move Y people (up to a maximum M, as de

If gridlock is a major issue now, self-driving vehicles won't help in a major way, since you still need X square feet to move Y people (up to a maximum M, as defined by the size of a vehicle) Z miles. Pushing more individual cars onto buses would help in this situation, but not as much as a dedicated subway line that is less impacted by vehicular traffic flows. Self-driving cars would help by removing some drivers not paying attention and causing additional congestion (eg: not moving on green lights or causing accidents).