The thing you're describing is called a train.
Compare the above to hop in my car, drive to the freeway, turn on self-driving, turn off self-driving once i get off the freeway, find parking near where i'm going and walk in.
As a society, we've done alot more in the name of convenience.
And you need a fleet of rental cars so that people can actually get to their destination.
What's the relative cost of all that vs. pavement?
If the cars are electric, I'm less sure.
Though your train of cars would likely have such low passenger density that a series of buses would be just as good. Special lanes just for buses are already a thing.
Commuter rail systems run at 2 minute headways or less. Long-distance trains mostly don't but that's largely due to excessive safety standards - for some reason we regulate trains to a much higher safety standard than cars. Even then, the higher top speeds of trains can make up for a certain amount of waiting and indirect routing. (Where I live, in London, trains are already faster than cars in the rush hour).
> What's the relative cost of all that vs. pavement?
When you include the land use and pollution? Cars can be cheaper for intercity distances when there's a lot of similarly-sized settlements, but within a city they waste too much space. And once you build cities for people rather than cars, cars lose a lot of their attraction for city-to-city travel as well, since you're in the same situation of having to change modes to get to your final destination.
That "some reason" is physics. According to a quick Google search, an average race car needs 400m of track length from 300 km/h to 0 km/h. A train will require something around 2500m, over 5x the distance, to brake from the same speed. Trains top out at -1.1m/s² deceleration, an ordinary car can get -10m/s² deceleration.
Part of the reason why is also that in a car, people are generally using their seatbelts - which means you can safely hit the brakes with full power. In a train, however, people will be walking around, standing, taking a dump on the loo - and no one will be using a belt. Unless you want to send people literally flying through the carriages, you can't go very much over that 1 m/s² barrier.
Because of this, you have the requirement of signalling blocks spaced in a way that a train at full speed can still come to a full stop before the next block signal. Also: a train can carry thousands of people. Have one train derail and crash into e.g. a bridge or crash with another train and you're looking with way, way, way more injuries and dead people than even a megacity could support, much less in a rural area.