We won't need as many of them but the ones we use will be almost constantly on the road, 20 cars on the road all the time is more traffic than 100 cars on the road 10% of the time and in people's garages the rest of the time
Why would 20 cars be constantly on the road? The cars would sit in parking lots, ready for a call. The actual road traffic, will not change. 1000 people going to work is 1000 people going to work irrespective whether they own the car.
The biggest change would be the lack of a need for parking. This will allow us to build more densely.
You'd have more cars constantly on the road because the smaller pool of cars has to also travel to where the people are. If I go from A to B and later from B to A, a robotaxi would also need to get to A and B when I need them. It really won't matter if they're in use or drove off to a parking lot somewhere else, that is extra traffic.
The amount of traffic will increase because people who couldn’t drive before and would ride with other people or use public transit (eg. children and the elderly) can now hail cheap autonomous cars, inefficiently using an entire car for their trip.
Induced demand economics. Make something cheaper and people use more of it.
If Autonomous cars make ride hailing cheaper we’ll see an explosion in its use, and traffic will increase as cars are space inefficient and road size fixed.
Wait, are there 1000 people going to work, and then the car parking outside of work? Or are those cars leaving where the people work to go elsewhere? the later creates more cars on the road. Sure those 1000 cars can go somewhere to park - but now we can't build much denser as we still need parking for the cars. Maybe we can move the cars out a bit for more density where people work, but then we need roads to get those cars back out.
Traffic and travel time are still a concern: Will I get to work in time for my shift? When I get home how much time will I have for dinner before [whatever you have planned that night]. When do I need to get into this car to make it to [whatever event]
If you are a single person working a flexible schedule (no mandatory meetings), with no other activities planned traffic and travel time are not a big deal. However if you have any life at all you will care about traffic and travel time because you have places to be. Watching netflix is not your goal it is how you kill time that you would prefer to do something else.
