Cities already tend to have limited parking. We might see more parking structures located in cheap out-of-the-way locations rather than near places people want to go. And street parking could go away in favor of consolidated parking structures, freeing up road space for both car traffic (with extra lanes) and foot traffic (widen sidewalks).
But I think it'll have an even larger effect on suburban areas. Shopping centers, strip malls, and similar will no longer need to have massive flat single-story parking lots, freeing up a huge amount of space. Likewise for major employers, and commuter parking lots for mass transit.
Instead of 100 people owning 100 cars they drive 5% of the time, they could own 10 summonable cars that drive them around 50% of the time.
The first scenario requires 95 parking spots. The second only 5. There is still as much traffic on the roads, and as much transport work being done, but most of the space now needed for parking can be put to other use.
No because you have to account for peak usage and have the capacity for it. There will be car savings, but the math wont be as simple as you say it is.
Have staggered work start and end times and "peak usage" will be a less pronounced peak. Also add in more home offices. I've no doubt that in 20 years car ownership will be a fraction of what it is today. Everything points in that direction and nothing opposes it.
> Have staggered work start and end times and "peak usage" will be a less pronounced peak.
This would have benefits today, but still rarely happens. A very small fraction of massive businesses have shift workers do this to more efficiently handle the volume that transitions between shifts would otherwise cause, but the vast majority of businesses do not. I don't think self-driving cars would change this.
> Also add in more home offices.
This would help today as well, but I don't think self-driving cars will change this either. (And if they do, it might not be in the direction you'd hope: self-driving cars might cause people to tolerate longer commutes.)
A taxi driver has a salary of, let's say, $40k a year. When that's removed the cost to travel in an autonomous car will be so low that it's lower than most forms of public transport with the benefit that it brings you door to door.
But I think it'll have an even larger effect on suburban areas. Shopping centers, strip malls, and similar will no longer need to have massive flat single-story parking lots, freeing up a huge amount of space. Likewise for major employers, and commuter parking lots for mass transit.