What I want is a way to rent a car for an hour or two, so that I can leave shopping items or child seats in the car while making stops around town.

AAA had car-sharing as a service nine years ago, but it and many of its competitors have closed:

https://oaklandside.org/2024/07/25/gig-will-shut-down-its-ca...

I think you're looking at $60 an hour which is not horrible (estimating Waymo avg is 3 rides / hour x $20 per ride)

I assume you mean a self-driving vehicle but if not: https://www.zipcar.com/cities

Like Waymo meets Zipcar?

That actually sorta? exists! Vay uses remotely teleoperated vehicles in Vegas to drop off your rental, then take it away once you're done.

https://vay.io/

This is the best combo possible. It feels like the ideal trade-off between the autonomy of car ownership and the flexibility of ride-sharing. I've been hearing about this concept for literally over a decade now.

I hope it expands quickly to the rest of the US.

You're kidding. This cannot be real. I can't wait to try it, if it is somehow real.